Input loop

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Task
Input loop
You are encouraged to solve this task according to the task description, using any language you may know.
Input loop is part of Short Circuit's Console Program Basics selection.
Task

Read from a text stream either word-by-word or line-by-line until the stream runs out of data.

The stream will have an unknown amount of data on it.

AArch64 Assembly[edit]

Works with: as version Raspberry Pi 3B version Buster 64 bits
/* ARM assembly AARCH64 Raspberry PI 3B */
/*  program inputLoop64.s   */

/*******************************************/
/* Constantes file                         */
/*******************************************/
/* for this file see task include a file in language AArch64 assembly*/
.include "../includeConstantesARM64.inc"

.equ BUFSIZE,  10000
.equ LINESIZE, 100

/*********************************/
/* Initialized data              */
/*********************************/
.data
szMessErreur:     .asciz "Erreur ouverture fichier input.\n"
szMessErreur1:    .asciz "Erreur fermeture fichier.\n"
szMessErreur2:    .asciz "Erreur lecture fichier.\n"
szCarriageReturn: .asciz "\n"
szMessEndLine:    .asciz "<<<<<< End line.\n"

szMessCodeErr: .asciz "Error code décimal :  @ \n"

szNameFileInput:    .asciz "input.txt"

/*******************************************/
/* DONNEES NON INITIALISEES                */
/*******************************************/ 
.bss
sZoneConv:    .skip 24
sBuffer:      .skip BUFSIZE 
sBufferWord:  .skip LINESIZE
/**********************************************/
/* -- Code section                            */
/**********************************************/
.text            
.global main    
main:
    /* open file */
    mov x0,AT_FDCWD
    ldr x1,qAdrszNameFileInput     // file name
    mov x2,O_RDONLY                //  flags   
    mov x3,0                       // mode 
    mov x8,OPEN                    // call system OPEN
    svc 0 
    cmp x0,0                       // open error ?
    ble erreur
    /* read file  */
    mov x9,x0                      // save File Descriptor
    ldr x1,qAdrsBuffer             // buffer address 
    mov x2,BUFSIZE                 // buffer size
    mov x8,READ                    // call system  READ
    svc 0 
    cmp x0,0                       // read error ?
    ble erreur2
    mov x2,x0                      // length read characters
    /* buffer analyze   */
    ldr x3,qAdrsBuffer             // buffer address
    ldr x5,qAdrsBufferWord         // buffer address
    mov x7,0                       // word byte counter
    mov x4,0                       // byte counter
    mov x10,1
1:
    ldrb w6,[x3,x4]                // load byte buffer
    cmp x6,' '                     // space ?
    csel x8,xzr,x10,eq             // yes  0-> x8
    beq 2f
    cmp x6,0xA                     // end line ?
    csel x8,x10,xzr,eq             // yes 1 -> x8
    beq 2f
    cmp x6,0xD                     // end line ?
    csel x8,x10,xzr,eq
    beq 3f
    strb w6,[x5,x7]                // store byte
    add x7,x7,1                    // increment word byte counter
    b 4f
2:                                 // word end
    cmp x7,0
    beq 3f
    mov x6,0                       // store 0 final
    strb w6,[x5,x7]
    mov x0,x5                      // display word
    bl affichageMess
    ldr x0,qAdrszCarriageReturn
    bl affichageMess
    mov x7,0                       // raz word byte counter 
3:
    cmp x8,1                       // end line ?
    bne 4f
    ldr x0,qAdrszMessEndLine
    bl affichageMess
4:       
    add x4,x4,1                    // increment read buffer counter
    cmp x4,x2                      // end bytes ?
    blt 1b                         // no -> loop 

4:
    /* close imput file */
    mov x0,x9                      // Fd
    mov x8,CLOSE                   // call system CLOSE
    svc 0 
    cmp x0,0                       // close error ?
    blt erreur1

    mov x0,0                       // return code OK
    b 100f
erreur:
    ldr x1,qAdrszMessErreur 
    bl displayError
    mov x0,1                       // error return code
    b 100f
erreur1:    
    ldr x1,qAdrszMessErreur1   
    bl displayError
    mov x0,1                      // error return code
    b 100f
erreur2:
    ldr x1,qAdrszMessErreur2   
    bl displayError
    mov x0,1                      // error return code
    b 100f

100:                              // end program
    mov x8,EXIT
    svc 0 
qAdrszNameFileInput:      .quad szNameFileInput
qAdrszMessErreur:         .quad szMessErreur
qAdrszMessErreur1:        .quad szMessErreur1
qAdrszMessErreur2:        .quad szMessErreur2
qAdrszCarriageReturn:     .quad szCarriageReturn
qAdrszMessEndLine:        .quad szMessEndLine
qAdrsBuffer:              .quad sBuffer
qAdrsBufferWord:          .quad sBufferWord
/******************************************************************/
/*     display error message                                      */ 
/******************************************************************/
/* x0 contains error code */
/* x1 contains address error message    */
displayError:
    stp x2,lr,[sp,-16]!            // save  registers
    mov x2,x0                      // save error code
    mov x0,x1                      // display message error
    bl affichageMess
    mov x0,x2
    ldr x1,qAdrsZoneConv           // conversion error code
    bl conversion10S               // decimal conversion
    ldr x0,qAdrszMessCodeErr
    ldr x1,qAdrsZoneConv
    bl strInsertAtCharInc          // insert result at @ character
    bl affichageMess               // display message final
    ldp x2,lr,[sp],16              // restaur  2 registers
    ret                            // return to address lr x30
qAdrsZoneConv:        .quad sZoneConv
qAdrszMessCodeErr:    .quad szMessCodeErr
/********************************************************/
/*        File Include fonctions                        */
/********************************************************/
/* for this file see task include a file in language AArch64 assembly */
.include "../includeARM64.inc"

Action![edit]

PROC ReadStream(BYTE stream)
  CHAR ARRAY line(255)

  WHILE Eof(stream)=0
  DO
    InputSD(stream,line)
    PrintE(line)
  OD
RETURN

PROC Main()
  BYTE streamId=[1]

  Close(streamId)
  Open(streamId,"H6:INPUT_PU.ACT",4)
  PrintE("Reading from stream...") PutE()
  ReadStream(streamId)
  Close(streamId)
RETURN
Output:

Screenshot from Atari 8-bit computer

Reading from stream...

PROC ReadStream(BYTE stream)
  CHAR ARRAY line(255)

  WHILE Eof(stream)=0
  DO
    InputSD(stream,line)
    PrintE(line)
  OD
RETURN

PROC Main()
  BYTE streamId=[1]

  Close(streamId)
  Open(streamId,"H6:INPUT_PU.ACT",4)
  PrintE("Reading from stream...") PutE()
  ReadStream(streamId)
  Close(streamId)
RETURN

Ada[edit]

This example reads in a text stream from standard input line by line and writes the output to standard output.

with Ada.Text_Io; use Ada.Text_Io;

procedure Read_Stream is
   Line : String(1..10);
   Length : Natural;
begin
   while not End_Of_File loop
      Get_Line(Line, Length); -- read up to 10 characters at a time
      Put(Line(1..Length));
      -- The current line of input data may be longer than the string receiving the data.
      -- If so, the current input file column number will be greater than 0
      -- and the extra data will be unread until the next iteration.
      -- If not, we have read past an end of line marker and col will be 1
      if Col(Current_Input) = 1 then
         New_Line;
      end if;
   end loop;
end Read_Stream;

Aime[edit]

void
read_stream(file f)
{
    text s;

    while (f_line(f, s) != -1) {
        # the read line available as -s-
    }
}

ALGOL 68[edit]

For file consisting of just one page - a typical linux/unix file:

main:(
  PROC raise logical file end = (REF FILE f) BOOL: ( except logical file end );
  on logical file end(stand in, raise logical file end);
  DO
    print(read string);
    read(new line);
    print(new line)
  OD;
  except logical file end: 
    SKIP
)

For multi page files, each page is seekable with PROC set = (REF FILE file, INT page, line, char)VOID: ~. This allows rudimentary random access where each new page is effectively a new record.

main:(
  PROC raise logical file end = (REF FILE f) BOOL: ( except logical file end );
  on logical file end(stand in, raise logical file end);
  DO
    PROC raise page end = (REF FILE f) BOOL: ( except page end );
    on page end(stand in, raise page end);
    DO
      print(read string);
      read(new line);
      print(new line)
    OD;
    except page end: 
      read(new page);
      print(new page)
  OD;
  except logical file end: 
    SKIP
)

The boolean functions physical file ended(f), logical file ended(f), page ended(f) and line ended(f) are also available to indicate the end of a file, page and line.

ALGOL W[edit]

begin
    string(80) line;
    % allow the program to continue after reaching end-of-file %
    % without this, end-of-file would cause a run-time error   %
    ENDFILE := EXCEPTION( false, 1, 0, false, "EOF" );
    % read lines until end of file                             %
    read( line );
    while not XCPNOTED(ENDFILE) do begin
        write( line );
        read(  line )
    end        
end.

AmigaE[edit]

CONST BUFLEN=1024, EOF=-1

PROC consume_input(fh)
  DEF buf[BUFLEN] : STRING, r
  REPEAT
    /* even if the line si longer than BUFLEN,
       ReadStr won't overflow; rather the line is
       "splitted" and the remaining part is read in
       the next ReadStr */
    r := ReadStr(fh, buf)
    IF buf[] OR (r <> EOF)
      -> do something
      WriteF('\s\n',buf)
    ENDIF
  UNTIL r=EOF
ENDPROC

PROC main()
  DEF fh

  fh := Open('basicinputloop.e', OLDFILE)
  IF fh
    consume_input(fh)
    Close(fh)
  ENDIF
ENDPROC

APL[edit]

Works with: GNU APL
      h   (⎕fio['read_text'] 'corpus/sample1.txt')
      h
7 49
      ]boxing 8
      h
────────────────────────────────────────────────┐
This is some sample text.                        
The text itself has multiple lines, and          
the text has some words that occur multiple times
in the text.                                     
                                                 
This is the end of the text.                     
                                                 
└─────────────────────────────────────────────────┘

ARM Assembly[edit]

Works with: as version Raspberry Pi
/* ARM assembly Raspberry PI  */
/*  program inputLoop.s   */

/* REMARK 1 : this program use routines in a include file 
   see task Include a file language arm assembly 
   for the routine affichageMess conversion10 
   see at end of this program the instruction include */

/*********************************************/
/*constantes                                */
/********************************************/
.equ STDOUT, 1     @ Linux output console
.equ EXIT,   1     @ Linux syscall
.equ READ,   3
.equ WRITE,  4
.equ OPEN,   5
.equ CLOSE,  6
.equ CREATE,  8
/*  file */
.equ O_RDONLY,    0x0        @ open for reading only

.equ BUFSIZE,  10000
.equ LINESIZE, 100

/*********************************/
/* Initialized data              */
/*********************************/
.data
szMessErreur:     .asciz "Erreur ouverture fichier input.\n"
szMessErreur1:    .asciz "Erreur fermeture fichier.\n"
szMessErreur2:    .asciz "Erreur lecture fichier.\n"
szCarriageReturn: .asciz "\n"
szMessEndLine:    .asciz "<<<<<< End line.\n"

szNameFileInput:    .asciz "input.txt"

/*******************************************/
/* DONNEES NON INITIALISEES                */
/*******************************************/ 
.bss
sBuffer:      .skip BUFSIZE 
sBufferWord:  .skip LINESIZE
/**********************************************/
/* -- Code section                            */
/**********************************************/
.text            
.global main    
main:
    /* open file */
    ldr r0,iAdrszNameFileInput      @ file name
    mov r1,#O_RDONLY                @  flags   
    mov r2,#0                       @ mode 
    mov r7,#OPEN                    @ call system OPEN
    svc #0 
    cmp r0,#0                       @ open error ?
    ble erreur
    /* read file  */
    mov r9,r0                       @ save File Descriptor
    ldr r1,iAdrsBuffer              @ buffer address 
    mov r2,#BUFSIZE                 @ buffer size
    mov r7, #READ                   @ call system  READ
    svc 0 
    cmp r0,#0                       @ read error ?
    ble erreur2
    mov r2,r0                       @ length read characters
    /* buffer analyze   */
    ldr r3,iAdrsBuffer              @ buffer address
    ldr r5,iAdrsBufferWord          @ buffer address
    mov r7,#0                       @ word byte counter
    mov r4,#0                       @ byte counter
1:
    ldrb r6,[r3,r4]                 @ load byte buffer
    cmp r6,#' '                     @ space ?
    moveq r8,#0                     @ yes
    beq 2f
    cmp r6,#0xA                     @ end line ?
    moveq r8,#1
    beq 2f
    cmp r6,#0xD                     @ end line ?
    beq 3f
    strb r6,[r5,r7]                 @ store byte
    add r7,#1                       @ increment word byte counter
    b 4f
2:                                  @ word end
    cmp r7,#0
    beq 3f
    mov r6,#0                       @ store 0 final
    strb r6,[r5,r7]
    mov r0,r5                       @ display word
    bl affichageMess
    ldr r0,iAdrszCarriageReturn
    bl affichageMess
    mov r7,#0                       @ raz word byte counter 
3:
    cmp r8,#1                       @ end line ?
    bne 4f
    ldr r0,iAdrszMessEndLine
    bl affichageMess
4:       
    add r4,#1                       @ increment read buffer counter
    cmp r4,r2                       @ end bytes ?
    blt 1b                          @ no -> loop 

4:
    /* close imput file */
    mov r0,r9                       @ Fd
    mov r7, #CLOSE                  @ call system CLOSE
    svc 0 
    cmp r0,#0                       @ close error ?
    blt erreur1


    mov r0,#0     @ return code OK
    b 100f
erreur:
    ldr r1,iAdrszMessErreur 
    bl displayError
    mov r0,#1       @ error return code
    b 100f
erreur1:    
    ldr r1,iAdrszMessErreur1   
    bl displayError
    mov r0,#1       @ error return code
    b 100f
erreur2:
    ldr r1,iAdrszMessErreur2   
    bl displayError
    mov r0,#1       @ error return code
    b 100f


100:        @ end program
    mov r7, #EXIT 
    svc 0 
iAdrszNameFileInput:      .int szNameFileInput
iAdrszMessErreur:         .int szMessErreur
iAdrszMessErreur1:        .int szMessErreur1
iAdrszMessErreur2:        .int szMessErreur2
iAdrszCarriageReturn:     .int szCarriageReturn
iAdrszMessEndLine:        .int szMessEndLine
iAdrsBuffer:              .int sBuffer
iAdrsBufferWord:          .int sBufferWord
/***************************************************/
/*      ROUTINES INCLUDE                           */
/***************************************************/
.include "../affichage.inc"
Output:
word1
word2
word3
<<<<<< End line.
Line2w1
line2w2
<<<<<< End line.
Oneword
<<<<<< End line.
<<<<<< End line.
AfterEmptyLine
<<<<<< End line.

AutoHotkey[edit]

This example reads the text of a source file line by line and writes the output to a destination file.

Loop, Read, Input.txt, Output.txt
{
   FileAppend, %A_LoopReadLine%`n
}

AWK[edit]

This just reads lines from stdin and prints them until EOF is read.

{ print $0 }

or, more idiomatic:

1

BASIC[edit]

BASIC256[edit]

f = freefile
open f, "test.txt"

while not eof(f)
	linea$ = readline(f)
	print linea$	# echo to the console
end while
close f
end

OxygenBasic[edit]

uses Console
uses ParseUtil
string s=getfile "t.txt"
int le=len s
int i=1
while i<le
  print GetNextLine(s,i) cr
wend
pause

QBasic[edit]

Works with: QBasic
Works with: QuickBasic
OPEN "test.txt" FOR INPUT AS #1

WHILE NOT EOF(1)
    INPUT #1, linea$
    PRINT linea$	' echo to the console
WEND

CLOSE #1
END

True BASIC[edit]

OPEN #1: NAME "test.txt", ACCESS INPUT

DO
   LINE INPUT #1: linea$
   PRINT linea$                   ! echo to the console
LOOP UNTIL END #1

CLOSE #1
END

Yabasic[edit]

filename$ = "test.txt"
f = open(filename$)

if not f error "Could not open '" + filename$ + "' for reading"
while(not eof(f)) 
    line input #f linea$
    print linea$	// echo to the console
wend

close f
end

Applesoft BASIC[edit]

100 INPUT "FILENAME:";F$
110 D$ = CHR$(4)
120 PRINT D$"VERIFY"F$
130 PRINT D$"OPEN"F$
140 PRINT D$"READ"F$
150 ONERR GOTO 190

160 GET C$
170 PRINT CHR$(0)C$;
180 GOTO 160

190 POKE 216,0
200 IF PEEK(222) <> 5 THEN RESUME
210 PRINT D$"CLOSE"F$

BaCon[edit]

'--- some generic header file to give it a real test
PRINT "Enter any file name you want to read  ex: /usr/include/X11/X.h"
INPUT filename$

text$  = LOAD$(filename$)
SPLIT text$ BY NL$ TO TOK$ SIZE dim
i = 0

'---dynamic index  the end of an array is always null terminated
	WHILE (TOK$[i] ISNOT NULL) 
		PRINT TOK$[i]
		INCR i
	WEND

BBC BASIC[edit]

This specifically relates to console input (stdin).

      STD_INPUT_HANDLE = -10
      STD_OUTPUT_HANDLE = -11
      SYS "GetStdHandle", STD_INPUT_HANDLE TO @hfile%(1)
      SYS "GetStdHandle", STD_OUTPUT_HANDLE TO @hfile%(2)
      SYS "SetConsoleMode", @hfile%(1), 0
      *INPUT 13
      *OUTPUT 14
      REPEAT
        INPUT A$
        PRINT A$
      UNTIL FALSE

Commodore BASIC[edit]

This example should generally work across all Commodore models. It is important to note that when using the reserved variable STATUS (or ST for short) to detect the end of file marker (bit 6), the KERNAL updates this variable based on any previous I/O operation, including the OPEN command, but makes no indication as to which I/O access the status applies to. Therefore, if using the disk drive, it is best to open the command file number and channel (15) before opening the actual file on disk, and leave the command channel open while performing the operations to open the file and access it as shown in the example.

10 rem input loop - rosetta code
11 rem open command channel, clear screen, switch to lower case
12 open 15,8,15
15 print chr$(147);chr$(14):f$=""

20 input "Enter filename";f$
25 if f$="" then end

30 open 5,8,5,f$+",s,r"
40 gosub 1000
50 if er=62 then print "That file is not found... Try again.":close 5:goto 20
60 if er<>0 then print "There was an unexpected error.":close 5:gosub 1100

70 get#5,a$
80 if st and 64 then close 5:close 15:end
90 print a$;:goto 70

1000 rem check command channel for error
1005 rem error number, error msg$, track number, sector number
1010 input#15,er,er$,tk,sc
1020 return

1100 rem print error
1110 print:print er;"- ";er$;" track:";tk;"sector:";sc
1120 return

IS-BASIC[edit]

100 PROGRAM "Type.bas"
110 TEXT 80
120 INPUT PROMPT "File name: ":F$
130 WHEN EXCEPTION USE IOERROR
140   OPEN #1:F$ ACCESS INPUT
150   DO
160     LINE INPUT #1,IF MISSING EXIT DO:F$
170     PRINT F$
180   LOOP
190   CLOSE #1
200 END WHEN 
210 HANDLER IOERROR
220   PRINT EXSTRING$(EXTYPE)
230   END
240 END HANDLER

Alternate solution:

100 PROGRAM "Type.bas"
110 INPUT PROMPT "File name: ":F$
120 WHEN EXCEPTION USE IOERROR
130   OPEN #1:F$
140   COPY FROM #1 TO #0
150   CLOSE #1
160 END WHEN
170 HANDLER IOERROR
180   PRINT EXSTRING$(EXTYPE)
190   CLOSE #1
200 END HANDLER

uBasic/4tH[edit]

If Set (a, Open ("myfile.bas", "r")) < 0 Then Print "Cannot open \qmyfile.bas\q" : End

Do While Read (a)
  Print Show(Tok(0))
Loop

Close a

This version tokenizes the line read and prints all individual words.

If Set (a, Open ("myfile.bas", "r")) < 0 Then Print "Cannot open \qmyfile.bas\q" : End

Do While Read (a)                      ' get next line
  Do
    p = Here()                         ' save cursor position
    s = Tok(Ord(" "))                  ' tokenize next word
  Until p = Here()                     ' quit if cursor didn't progress
    If Len(s) Then Print Show(s)       ' print only full words
  Loop                                 ' next word
Loop                                   ' next line

Close a

Batch File[edit]

for /f %%i in (file.txt) do if %%i@ neq @ echo %%i

Bracmat[edit]

This example first creates a test file with three lines. It then opens the file in read mode, sets the string of break characters and then reads the file token by token, where tokens are delimeted by break characters. Finally, the file position is set to an invalid value, which closes the file.

( put$("This is
a three line
text","test.txt",NEW)
& fil$("test.txt",r)
& fil$(,STR," \t\r\n")
& 0:?linenr
&   whl
  ' ( fil$:(?line.?breakchar)
    &   put
      $ ( str
        $ ( "breakchar:"
            ( !breakchar:" "&SP
            | !breakchar:\t&"\\t"
            | !breakchar:\r&"\\r"
            | !breakchar:\n&"\\n"
            | !breakchar:&EOF
            )
            ", word "
            (1+!linenr:?linenr)
            ":"
            !line
            \n
          )
        )
    )
& (fil$(,SET,-1)|out$"file closed")
);
Output:
breakchar:SP, word 1:This
breakchar:\n, word 2:is
breakchar:SP, word 3:a
breakchar:SP, word 4:three
breakchar:\n, word 5:line
breakchar:EOF, word 6:text
file closed

C[edit]

Reads arbitrarily long line each time and return a null-terminated string. Caller is responsible for freeing the string.

#include <stdlib.h>
#include <stdio.h>

char *get_line(FILE* fp)
{
	int len = 0, got = 0, c;
	char *buf = 0;

	while ((c = fgetc(fp)) != EOF) {
		if (got + 1 >= len) {
			len *= 2;
			if (len < 4) len = 4;
			buf = realloc(buf, len);
		}
		buf[got++] = c;
		if (c == '\n') break;
	}
	if (c == EOF && !got) return 0;

	buf[got++] = '\0';
	return buf;
}

int main()
{
	char *s;
	while ((s = get_line(stdin))) {
		printf("%s",s);
		free(s);
	}
	return 0;
}

C#[edit]

using System;
using System.IO;

class Program
{
    static void Main(string[] args)
    {
        // For stdin, you could use
        // new StreamReader(Console.OpenStandardInput(), Console.InputEncoding)

        using (var b = new StreamReader("file.txt"))
        {
            string line;
            while ((line = b.ReadLine()) != null)
                Console.WriteLine(line);
        }
    }
}

C++[edit]

The following functions send the words resp. lines to a generic output iterator.

#include <istream>
#include <string>
#include <vector>
#include <algorithm>
#include <iostream>
#include <iterator>

// word by word
template<class OutIt>
void read_words(std::istream& is, OutIt dest)
{
  std::string word;
  while (is >> word)
  {
    // send the word to the output iterator
    *dest = word;
  }
}

// line by line:
template<class OutIt>
void read_lines(std::istream& is, OutIt dest)
{
  std::string line;
  while (std::getline(is, line))
  {
    // store the line to the output iterator
    *dest = line;
  }
}

int main()
{
  // 1) sending words from std. in std. out (end with Return)
  read_words(std::cin, 
             std::ostream_iterator<std::string>(std::cout, " "));

  // 2) appending lines from std. to vector (end with Ctrl+Z)
  std::vector<std::string> v;
  read_lines(std::cin, std::back_inserter(v));
  
  return 0;
}

An alternate way to read words or lines is to use istream iterators:

template<class OutIt>
void read_words(std::istream& is, OutIt dest)
{
    typedef std::istream_iterator<std::string> InIt;
    std::copy(InIt(is), InIt(),
              dest);
}

namespace detail 
{
    struct ReadableLine : public std::string 
    { 
        friend std::istream & operator>>(std::istream & is, ReadableLine & line)
        {   
            return std::getline(is, line);
        }
    };
}

template<class OutIt>
void read_lines(std::istream& is, OutIt dest)
{
    typedef std::istream_iterator<detail::ReadableLine> InIt;
    std::copy(InIt(is), InIt(),
              dest);
}

Clojure[edit]

(defn basic-input [fname]
  (line-seq (java.io.BufferedReader. (java.io.FileReader. fname))))

COBOL[edit]

Works with: GNU Cobol version 2.0
Works with: Visual COBOL
       IDENTIFICATION DIVISION.
       PROGRAM-ID. input-loop.
       
       ENVIRONMENT DIVISION.
       INPUT-OUTPUT SECTION.
       FILE-CONTROL.
           SELECT in-stream ASSIGN TO KEYBOARD *> or any other file/stream
               ORGANIZATION LINE SEQUENTIAL
               FILE STATUS in-stream-status.
               
       DATA DIVISION.
       FILE SECTION.
       FD  in-stream.
       01  stream-line                 PIC X(80).
       
       WORKING-STORAGE SECTION.
       01  in-stream-status            PIC 99.
           88  end-of-stream           VALUE 10.
       
       PROCEDURE DIVISION.
           OPEN INPUT in-stream
           
           PERFORM UNTIL EXIT
               READ in-stream
                   AT END
                       EXIT PERFORM
               END-READ
               DISPLAY stream-line
           END-PERFORM
           
           CLOSE in-stream
           .
       END PROGRAM input-loop.

Common Lisp[edit]

(defun basic-input (filename)
    (with-open-file (stream (make-pathname :name filename) :direction :input)
        (loop for line = (read-line stream nil nil)
            while line
            do (format t "~a~%" line))))

D[edit]

void main() {
    import std.stdio;

    immutable fileName = "input_loop1.d";

    foreach (const line; fileName.File.byLine) {
        pragma(msg, typeof(line)); // Prints: const(char[])
        // line is a transient slice, so if you need to
        // retain it for later use, you have to .dup or .idup it.
        line.writeln; // Do something with each line.
    }

    // Keeping the line terminators:
    foreach (const line; fileName.File.byLine(KeepTerminator.yes)) {
        // line is a transient slice.
        line.writeln;
    }

    foreach (const string line; fileName.File.lines) {
        // line is a transient slice.
        line.writeln;
    }
}
Library: Tango
import tango.io.Console;
import tango.text.stream.LineIterator;

void main (char[][] args) {
    foreach (line; new LineIterator!(char)(Cin.input)) {
        // do something with each line
    }
}
Library: Tango
import tango.io.Console;
import tango.text.stream.SimpleIterator;

void main (char[][] args) {
    foreach (word; new SimpleIterator!(char)(" ", Cin.input)) {
        // do something with each word
    }
}

Note that foreach variables 'line' and 'word' are transient slices. If you need to retain them for later use, you should .dup them.

Delphi[edit]

program InputLoop;

{$APPTYPE CONSOLE}

uses SysUtils, Classes;

var
  lReader: TStreamReader; // Introduced in Delphi XE
begin
  lReader := TStreamReader.Create('input.txt', TEncoding.Default);
  try
    while lReader.Peek >= 0 do
      Writeln(lReader.ReadLine);
  finally
    lReader.Free;
  end;
end.

Déjà Vu[edit]

while /= :eof dup !read-line!stdin:
	!print( "Read a line: " !decode!utf-8 swap )
drop
!print "End of file."

EasyLang[edit]

repeat
  l$ = input
  until error = 1
  print l$
.

Eiffel[edit]

Works with: Eiffel Studio version 6.6
note
	description : "{
There are several examples included, including input from a text file,
simple console input and input from standard input explicitly.
See notes in the code for details.

Examples were compile using Eiffel Studio 6.6 with only the default
class libraries.
}"

class APPLICATION

create
	make

feature

	make
		do
			-- These examples show non-console input (a plain text file)
			-- with end-of-input handling.
			read_lines_from_file
			read_words_from_file

			-- These examples use simplified input from 'io', that
			-- handles the details of whether it's stdin or not
			-- They terminate on a line (word) of "q"
			read_lines_from_console_with_termination
			read_words_from_console_with_termination

			-- The next examples show reading stdin explicitly
			-- as if it were a text file.  It expects and end of file
			-- termination and so will loop indefinitely unless reading
			-- from a pipe or your console can send an EOF.
			read_lines_from_stdin
			read_words_from_stdin

			-- These examples use simplified input from 'io', that
			-- handles the details of whether it's stdin or not,
			-- but have no explicit termination
			read_lines_from_console_forever
			read_words_from_console_forever
		end

	--|--------------------------------------------------------------

	read_lines_from_file
			-- Read input from a text file
			-- Echo each line of the file to standard output.
			--
			-- Some language examples omit file open/close operations
			-- but are included here for completeness.  Additional error
			-- checking would be appropriate in production code.
		local
			tf: PLAIN_TEXT_FILE
		do
			print ("Reading lines from a file%N")
			create tf.make ("myfile") -- Create a file object
			tf.open_read -- Open the file in read mode

			-- The actual input loop

			from
			until tf.end_of_file
			loop
				tf.read_line
				print (tf.last_string + "%N")
			end

			tf.close -- Close the file
		end

	--|--------------------------------------------------------------

	read_words_from_file
			-- Read input from a text file
			-- Echo each word of the file to standard output on a 
			-- separate line.
			--
			-- Some language examples omit file open/close operations
			-- but are included here for completeness.  Additional error
			-- checking would be appropriate in production code.
		local
			tf: PLAIN_TEXT_FILE
		do
			print ("Reading words from a file%N")
			create tf.make ("myfile") -- Create a file object
			tf.open_read -- Open the file in read mode

			-- The actual input loop

			from
			until tf.end_of_file
			loop
				-- This instruction is the only difference between this
				-- example and the read_lines_from_file example
				tf.read_word
				print (tf.last_string + "%N")
			end

			tf.close -- Close the file
		end

	--|--------------------------------------------------------------

	read_lines_from_console_with_termination
			-- Read lines from console and echo them back to output
			-- until the line contains only the termination key 'q'
			--
			-- 'io' is acquired through inheritance from class ANY,
			-- the top of all inheritance hierarchies.
		local
			the_cows_come_home: BOOLEAN
		do
			print ("Reading lines from console%N")
			from
			until the_cows_come_home
			loop
				io.read_line
				if io.last_string ~ "q" then
					the_cows_come_home := True
					print ("Mooooo!%N")
				else
					print (io.last_string)
					io.new_line
				end
			end
		end

	--|--------------------------------------------------------------

	read_words_from_console_with_termination
			-- Read words from console and echo them back to output, one
			-- word per line, until the line contains only the 
			-- termination key 'q'
			--
			-- 'io' is acquired through inheritance from class ANY,
			-- the top of all inheritance hierarchies.
		local
			the_cows_come_home: BOOLEAN
		do
			print ("Reading words from console%N")
			from
			until the_cows_come_home
			loop
				io.read_word
				if io.last_string ~ "q" then
					the_cows_come_home := True
					print ("Mooooo!%N")
				else
					print (io.last_string)
					io.new_line
				end
			end
		end

	--|--------------------------------------------------------------

	read_lines_from_console_forever
			-- Read lines from console and echo them back to output
			-- until the program is terminated externally
			--
			-- 'io' is acquired through inheritance from class ANY,
			-- the top of all inheritance hierarchies.
		do
			print ("Reading lines from console (no termination)%N")
			from
			until False
			loop
				io.read_line
				print (io.last_string + "%N")
			end
		end

	--|--------------------------------------------------------------

	read_words_from_console_forever
			-- Read words from console and echo them back to output, one 
			-- word per line until the program is terminated externally
			--
			-- 'io' is acquired through inheritance from class ANY,
			-- the top of all inheritance hierarchies.
		do
			print ("Reading words from console (no termination)%N")
			from
			until False
			loop
				io.read_word
				print (io.last_string + "%N")
			end
		end

	--|--------------------------------------------------------------

	read_lines_from_stdin
			-- Read input from a stream on standard input
			-- Echo each line of the file to standard output.
			-- Note that we treat standard input as if it were a plain 
			-- text file
		local
			tf: PLAIN_TEXT_FILE
		do
			print ("Reading lines from stdin (EOF termination)%N")
			tf := io.input

			from
			until tf.end_of_file
			loop
				tf.read_line
				print (tf.last_string + "%N")
			end
		end

	--|--------------------------------------------------------------

	read_words_from_stdin
			-- Read input from a stream on standard input
			-- Echo each word of the file to standard output on a new 
			-- line
			-- Note that we treat standard input as if it were a plain 
			-- text file
		local
			tf: PLAIN_TEXT_FILE
		do
			print ("Reading words from stdin (EOF termination)%N")
			tf := io.input

			from
			until tf.end_of_file
			loop
				tf.read_line
				print (tf.last_string + "%N")
			end
		end

end

Elena[edit]

ELENA 4.x:

Using ReaderEnumerator

import system'routines;
import system'io;
import extensions'routines;
 
public program()
{
    ReaderEnumerator.new(File.assign:"file.txt").forEach(printingLn)
}

Using loop statement

import system'io;
 
public program()
{
    using(var reader := File.assign:"file.txt".textreader())
    {
        while (reader.Available)
        {
           console.writeLine(reader.readLine())
        }
    }
}

Elixir[edit]

defmodule RC do
  def input_loop(stream) do
    case IO.read(stream, :line) do
      :eof -> :ok
      data -> IO.write data
              input_loop(stream)
    end
  end
end

path = hd(System.argv)
File.open!(path, [:read], fn stream -> RC.input_loop(stream) end)

Erlang[edit]

% Implemented by Arjun Sunel
-module(read_files).
-export([main/0]).

main() ->
	Read = fun (Filename) -> {ok, Data} = file:read_file(Filename), Data end,
	Lines = string:tokens(binary_to_list(Read("read_files.erl")), "\n"),
	lists:foreach(fun (Y) -> io:format("~s~n", [Y]) end, lists:zipwith(fun(X,_)->X end, Lines, lists:seq(1, length(Lines)))).

ERRE[edit]

input from stdio

     LOOP
       INPUT(LINE,A$)
       PRINT(A$)
       EXIT IF <condition> ! condition to be implemented to
                           ! to avoid and endless loop
     END LOOP

reading a text file line by line

     OPEN("I",#1,FILENAME$)
     WHILE NOT EOF(1)
         INPUT(LINE,#1,A$)
         PRINT(A$)
     END WHILE 
     CLOSE(1)

Note: with GET(#1) you can read character by character.

Euphoria[edit]

Process text stream line-by-line:

procedure process_line_by_line(integer fn)
    object line
    while 1 do
        line = gets(fn)
        if atom(line) then
            exit
        end if
        -- process the line
    end while
end procedure

F#[edit]

Using a sequence expression:

let lines_of_file file =
  seq { use stream = System.IO.File.OpenRead file
        use reader = new System.IO.StreamReader(stream)
        while not reader.EndOfStream do
          yield reader.ReadLine() }

The file is reopened every time the sequence is traversed and lines are read on-demand so this can handle arbitrarily-large files.

Factor[edit]

"file.txt" utf8 [ [ process-line ] each-line ] with-file-reader

Fantom[edit]

An input stream can be from a string or from a file. The method eachLine will divide the stream by linebreaks. The method readStrToken takes two arguments: a maximum size to read, and a function to decide when to stop reading - by default, it stops when it finds a white space.

class Main
{
  public static Void main ()
  {
    // example of reading by line
    str := "first\nsecond\nthird\nword"
    inputStream := str.in

    inputStream.eachLine |Str line|
    {
      echo ("Line is: $line")
    }

    // example of reading by word
    str = "first second third word"
    inputStream = str.in

    word := inputStream.readStrToken // reads up to but excluding next space
    while (word != null)
    {
      echo ("Word: $word")
      inputStream.readChar // skip over the preceding space!
      word = inputStream.readStrToken
    }
  }
}

Forth[edit]

Works with: GNU Forth
4096 constant max-line
: read-lines
  begin  stdin pad max-line read-line throw
  while  pad swap   \ addr len is the line of data, excluding newline
         2drop
  repeat ;

Fortran[edit]

Works with: Fortran version 90 and later

The code read line-by-line, but the maximum length of the line is limited (by a parameter)

program BasicInputLoop

  implicit none

  integer, parameter        :: in = 50, &
                               linelen = 1000
  integer                   :: ecode
  character(len=linelen)    :: l

  open(in, file="afile.txt", action="read", status="old", iostat=ecode)
  if ( ecode == 0 ) then
     do
        read(in, fmt="(A)", iostat=ecode) l
        if ( ecode /= 0 ) exit
        write(*,*) trim(l)
     end do
     close(in)
  end if

end program BasicInputLoop

FreeBASIC[edit]

' FB 1.05.0 Win64

Dim line_ As String  ' line is a keyword
Open "input.txt" For Input As #1 

While Not Eof(1)
  Input #1, line_
  Print line_  ' echo to the console
Wend

Close #1
Print
Print "Press any key to quit"
Sleep

Frink[edit]

while (line = readStdin[]) != undef
   println[line]

FutureBasic[edit]

Note: This code goes beyond simply specifying the file to open. It includes a dialog window that allows the user to select a text file to read. The entire contents of the file are read in at once, rather than line by line.

include "NSLog.incl"

local fn ReadTextFile
  CFURLRef    url
  CFStringRef string
  
  url = openpanel 1, @"Select text file..."
  if ( url )
    string = fn StringWithContentsOfURL( url, NSUTF8StringEncoding, NULL )
    if ( string )
      NSLog(@"%@",string)
    end if
  else
    // user cancelled
  end if
end fn

fn ReadTextFile

HandleEvents

gnuplot[edit]

The following gnuplot script echoes standard input to standard output line-by-line until the end of the stream.

!cat

It makes use of the ability of gnuplot to spawn shell commands. In that sense it might be considered cheating. Nevertheless, this is a valid gnuplot script that does meet the requirements of the task description.

It seems impossible to complete this task with just standard gnuplot commands.

Go[edit]

The following reads a line at a time from stdin.

package main

import (
	"bufio"
	"io"
	"log"
	"os"
)

func main() {
	in := bufio.NewReader(os.Stdin)
	for {
		s, err := in.ReadString('\n')
		if err != nil {
			// io.EOF is expected, anything else
			// should be handled/reported
			if err != io.EOF {
				log.Fatal(err)
			}
			break
		}
		// Do something with the line of text
		// in string variable s.
		_ = s
	}
}

Or, using bufio.Scanner you can read line at a time, word at a time, byte or Unicode code point at a time, or by any custom "split function".

package main

import (
	"bufio"
	"log"
	"os"
)

func main() {
	s := bufio.NewScanner(os.Stdin)
	// Select the split function, other ones are available
	// in bufio or you can provide your own.
	s.Split(bufio.ScanWords)
	for s.Scan() {
		// Get and use the next 'token'
		asBytes := s.Bytes() // Bytes does no alloaction
		asString := s.Text() // Text returns a newly allocated string
		_, _ = asBytes, asString
	}
	if err := s.Err(); err != nil {
		// Handle/report any error (EOF will not be reported)
		log.Fatal(err)
	}
}

Groovy[edit]

Solution:

def lineMap = [:]
System.in.eachLine { line, i ->
    lineMap[i] = line
}
lineMap.each { println it }
Test:
$ groovy -e 'def lineMap = [:]
> System.in.eachLine { line, i ->
>     lineMap[i] = line
> }
> lineMap.each { println it }' <<EOF
> 
> Whose woods these are I think I know
> His house is in the village tho'
> He will not see me stopping here
> To watch his woods fill up with snow
> EOF
Output:
1=
2=Whose woods these are I think I know
3=His house is in the village tho'
4=He will not see me stopping here
5=To watch his woods fill up with snow

Haskell[edit]

The whole contents of a file can be read lazily. The standard functions lines and words convert that lazily into the lists of lines resp. words. Usually, one wouldn't use extra routines for that, but just use readFile and then put 'lines' or words somewhere in the next processing step.

import System.IO

readLines :: Handle -> IO [String]
readLines h = do
  s <- hGetContents h
  return $ lines s

readWords :: Handle -> IO [String]
readWords h = do
  s <- hGetContents h
  return $ words s

HicEst[edit]

CHARACTER name='myfile.txt', string*1000

   OPEN(FIle=name, OLD, LENgth=bytes, IOStat=errorcode, ERror=9)

   DO line = 1, bytes  ! loop terminates with end-of-file error at the latest
      READ(FIle=name, IOStat=errorcode, ERror=9) string
      WRITE(StatusBar) string
   ENDDO

 9 WRITE(Messagebox, Name) line, errorcode

i[edit]

software {
	loop {
		read()
		errors {
			exit
		}
	}
}

Icon and Unicon[edit]

link str2toks
# call either words or lines depending on what you want to do.
procedure main()
   words()
end

procedure lines()
   while write(read())
end

procedure words()
   local line
   while line := read() do line ? every write(str2toks())
end

See str2toks

J[edit]

Script "read-input-until-eof.ijs":

#!/Applications/j602/bin/jconsole
NB. read input until EOF
((1!:1) 3)(1!:2) 4
exit ''

Example:

$ ./read-input-to-eof.ijs <<EOF
> abc
> def
> ghi
> now is the time for all good men ...
> EOF
abc
def
ghi
now is the time for all good men ...

Java[edit]

Some people prefer Scanner or BufferedReader, so a way with each is presented.

import java.io.InputStream;
import java.util.Scanner;

public class InputLoop {
    public static void main(String args[]) {
        // To read from stdin:
        InputStream source = System.in;

        /*
        Or, to read from a file:
        InputStream source = new FileInputStream(filename);

        Or, to read from a network stream:
        InputStream source = socket.getInputStream();
        */

        Scanner in = new Scanner(source);
        while(in.hasNext()){
            String input = in.next(); // Use in.nextLine() for line-by-line reading

            // Process the input here. For example, you could print it out:
            System.out.println(input);
        }
    }
}

Or

import java.io.BufferedReader;
import java.io.IOException;
import java.io.InputStreamReader;
import java.io.Reader;

public class InputLoop {
    public static void main(String args[]) {
        // To read from stdin:
        Reader reader = new InputStreamReader(System.in);

        /*
        Or, to read from a file:
        Reader reader = new FileReader(filename);

        Or, to read from a network stream:
        Reader reader = new InputStreamReader(socket.getInputStream());
        */

        try {
            BufferedReader inp = new BufferedReader(reader);
            while(inp.ready()) {
                int input = inp.read(); // Use in.readLine() for line-by-line

                // Process the input here. For example, you can print it out.
                System.out.println(input);
            }
        }  catch (IOException e) {
            // There was an input error.
        }
    }
}

JavaScript[edit]

Works with: SpiderMonkey
Works with: OSSP js

These implementations of JavaScript define a readline() function, so:

$ js -e 'while (line = readline()) { do_something_with(line); }' < inputfile
Works with: JScript

As above, this operates on standard input

var text_stream = WScript.StdIn;
var i = 0;

while ( ! text_stream.AtEndOfStream ) {
    var line = text_stream.ReadLine();
    // do something with line
    WScript.echo(++i + ": " + line);
}

jq[edit]

The jq program for reading and writing is simply the one-character program:

   .
For example, to echo each line of text in a file, one could invoke jq as follows:
jq -r -R . FILENAME
If the input file consists of well-formed JSON entities (including scalars), then the following invocation could be used to "pretty-print" the input:
jq . FILENAME

Other options, e.g. to emit JSON in compact form, also exist.

Jsish[edit]

/* Input loop in Jsish */

var line;
var cs = 0, ls = 0;

while (line = console.input()) { cs += line.length; ls += 1; }

printf("%d lines, %d characters\n", ls, cs);
Output:
prompt$ jsish input-loop.jsi <input-loop.jsi
8 lines, 159 characters

Julia[edit]

We create a text stream and read the lines from the stream one by one, printing them on screen. Note that the lines end by a newline, except the last one. The ending newlines are part of the strings returned by the function readline. Once the end of the stream is reached, readline returns an empty string.

stream = IOBuffer("1\n2\n3\n4\n\n6")

while !eof(stream)
    line = readline(stream)
    println(line)
end
Output:
1
2
3
4

6

Kotlin[edit]

// version 1.1

import java.util.*

fun main(args: Array<String>) {
    println("Keep entering text or the word 'quit' to end the program:")
    val sc = Scanner(System.`in`)
    val words = mutableListOf<String>()
    while (true) {
        val input: String = sc.next()
        if (input.trim().toLowerCase() == "quit") {
            if (words.size > 0) println("\nYou entered the following words:\n${words.joinToString("\n")}")
            return
        }
        words.add(input)
    }
}

Sample input/output:

Output:
Keep entering text or the word 'quit' to end the program:
The quick brown fox
jumps over the lazy dog
quit

You entered the following words:
The
quick
brown
fox
jumps
over
the
lazy
dog

Lang5[edit]

: read-lines do read . "\n" . eof if break then loop ;
: ==>contents
    '< swap open 'fh set fh fin read-lines fh close ;

'file.txt ==>contents

Lasso[edit]

local(
	myfile		= file('//path/to/file.txt'),
	textresult	= array
)

#myfile -> foreachline => {
	#textresult -> insert(#1)
}

#textresult -> join('<br />')

Result: This is line one I am the second line Here is line 3

Liberty BASIC[edit]

filedialog "Open","*.txt",file$
if file$="" then end
open file$ for input as #f
while not(eof(#f))
    line input #f, t$
    print t$
wend
close #f
end

LIL[edit]

From the canread.lil sample that ships with LIL.

#
# canread test (note that canread is not available in LIL/FPLIL itself
# but provided by the command line interfaces in main.c/lil.pas)
#
# You can either call this and enter lines directly (use Ctrl+Z/Ctrl+D
# to finish) or a redirect (e.g. lil canread.lil < somefile.txt)
#
# Normally this is how you are supposed to read multiple lines from
# the standard input using the lil executable.  For an alternative way
# that uses error catching via try see the eoferror.lil script.
#

set count 0
while {[canread]} {
    readline
    inc count
}
print $count lines
Output:
prompt$ lil canread.lil <canread.lil
19 lines

[edit]

There are several words which will return a line of input.

  • readline - returns a line as a list of words
  • readword - returns a line as a single word, or an empty list if it reached the end of file
  • readrawline - returns a line as a single word, with no characters escaped
while [not eof?] [print readline]

LSL[edit]

LSL doesn't have a File System, but it does have Notecards that function as read-only text files, and can be use as configuration files or data sources.

To test it yourself; rez a box on the ground, add the following as a New Script, create a notecard named "Input_Loop_Data_Source.txt", and put what ever data you want in it (in this case I just put a copy of the source code.)

string sNOTECARD = "Input_Loop_Data_Source.txt";
default {
	integer iNotecardLine = 0;
	state_entry() {
		llOwnerSay("Reading '"+sNOTECARD+"'"); 
		llGetNotecardLine(sNOTECARD, iNotecardLine);
	}
	dataserver(key kRequestId, string sData) {
		if(sData==EOF) {
			llOwnerSay("EOF");
		} else {
			llOwnerSay((string)iNotecardLine+": "+sData);
			llGetNotecardLine(sNOTECARD, ++iNotecardLine);
		}
	}
}
Output:
Reading 'Input_Loop_Data_Source.txt'
0: string sNOTECARD = "Input_Loop_Data_Source.txt";
1: default {
2: 	integer iNotecardLine = 0;
3: 	state_entry() {
4: 		llOwnerSay("Reading '"+sNOTECARD+"'"); 
5: 		llGetNotecardLine(sNOTECARD, iNotecardLine);
6: 	}
7: 	dataserver(key kRequestId, string sData) {
8: 		if(sData==EOF) {
9: 			llOwnerSay("EOF");
10: 		} else {
11: 			llOwnerSay((string)iNotecardLine+": "+sData);
12: 			llGetNotecardLine(sNOTECARD, ++iNotecardLine);
13: 		}
14: 	}
15: }
EOF

Lua[edit]

lines = {}
str = io.read()
while str do
    table.insert(lines,str)
    str = io.read()
end

Via generic for loop[edit]

Reads line-by-line via an iterator (from stdin). Substitute io.lines() with io.open(filename, "r"):lines() to read from a file.

lines = {}

for line in io.lines() do
    table.insert(lines, line) -- add the line to the list of lines
end

M2000 Interpreter[edit]

Document A$={1st Line
      2nd line
      3rd line
      }
Save.Doc A$, "test.txt", 0   ' 0 for utf16-le
\\ we use Wide for utf16-le \\ without it we open using ANSI
Open "test.txt" For Wide Input Exclusive as #N
      While Not Eof(#N) {
            Line Input #N, ThisLine$
            Print ThisLine$
      }
Close #N
Clear A$
Load.Doc A$, "test.txt"
\\ print proportional text, all lines
Report A$
\\ Print one line, non proportional
\\ using paragraphs
For i=0 to Doc.par(A$)-1
      Print Paragraph$(A$, i)
Next i
\\ List of current variables (in any scope, public only)
List

Maple[edit]

readinput:=proc(filename)
local line,file;
file:="";
line:=readline(filename);
while line<>0 do
line:=readline(filename);
file:=cat(file,line);
end do;
end proc;

MACRO-10[edit]

        TITLE Input Loop

COMMENT !
       Input-loop example, PDP-10 assembly language, kjx 2022.
           Assembler: MACRO-10   Operating system: TOPS-20

   This program opens the file "test.txt" and prints it's contents.
   
   Note that the PDP-10 is a word-addressable machine with 36bit words,
   and text-files use 7bit ASCII. That means one word fits 5 characters
   and the buffer length of 20 (octal!) makes room for 80 (decimal) char-
   acters.
   
   The system-call used, SIN%, can also read until a specific character
   (like CR) is seen, so reading one-line-at-a-time is also possible with
   minimal changes.  
!

        SEARCH MONSYM,MACSYM
        .REQUIRE SYS:MACREL

        STDAC.                          ;Define standard register names.

        ;;
        ;; Buffers and data:
        ;;

        PDLLEN==20
PDL:    BLOCK PDLLEN                    ;Callstack (for ERCAL later).

        MAXBUF==20                      ;Use 20 36bit words for buffer.
        MAXCHR==MAXBUF*5                ;One 36bit words fits 5 7bit bytes.
IN.BUF: BLOCK MAXBUF                    ;Buffer for lines read from file.

IN.JFN: BLOCK 1                         ;Space for file-descriptor (JFN)

        ;;
        ;; Execution begins here:
        ;;

GO::    RESET%                          ;Initialize process.
        MOVE  P,[IOWD PDLLEN,PDL]       ;Initialize stack.
	
        ;;
        ;; To open a file, we first have to get a file-handle (JFN):
        ;;

        MOVX  T1,GJ%OLD+GJ%SHT          ;Flags go into T1:
                                        ; GJ%OLD = File already exists.
                                        ; GJ%SHT = Short system call.
        HRROI T2,[ASCIZ /test.txt/]     ;File name goes to T2.
        GTJFN%                          ;Get a JFN for this file.
          ERJMPS ERROR                  ;  On error jump to ERROR.
        MOVEM T1,IN.JFN                 ;Save the JFN.
        
        ;;
        ;; Now we can open the file:
        ;;
        
        HRRZ  T1,IN.JFN                 ;Right half-word of JFN into T1 +
                                        ;zero out left half to get rid of
					;flags returned by GTJFN%.
        MOVX  T2,FLD(7,OF%BSZ)+OF%RD    ;7bit characters, read-only.
        OPENF%                          ;Open file.
          ERJMPS ERROR                  ;  On error jump to ERROR.

        ;;
        ;; Now we're reading MAXCHR 7bit bytes from that file
        ;; into IN.BUF and print that. If we'll see EOF, Q1 is
        ;; set to 1, and the loop is exited.
        ;;
        
        SETZ  Q1                        ;Clear Q1 (we use that as an EOF marker)
        DO.
          MOVE  T1,IN.JFN               ;Read from IN.JFN (opened file)
          HRROI T2,IN.BUF               ;and write into IN.BUF.
          MOVNI T3,MAXCHR               ;Read maximum of MAXCHR characters.
          SIN%                          ;Read string from file.
            ERCAL [ MOVE  T1,IN.JFN     ;  Error occured...
                    GTSTS%              ;  Get file status.
                    TXNN  T2,GS%EOF     ;  End-of-file reached?
                      JRST ERROR        ;    No: Something else happened...
                    MOVEI Q1,1          ;  Yes: Set Q1 to 1.
                    RET ]               ;  Continue.
          MOVEI T1,.PRIOU               ;Write to standard output.
          HRROI T2,IN.BUF               ;Buffer to write.
          ADDI  T3,MAXCHR               ;Substract chars read from
          MOVN  T3,T3                   ;maximum buffer length.
          SOUT%                         ;Print string.
          CAIN  Q1,1                    ;Is Q1 == 1?
            JRST ENDPRG                 ;  Yes: EOF was found above.
          LOOP.                         ;Q1 is 0, so no EOF, continue.
        ENDDO.
        
        ;;
        ;; ENDPRG: Close file and halt.
        ;;
        
ENDPRG: HRRZ  T1,IN.JFN                 ;Put JFN into T1.
        CLOSF%                          ;Close that file.
          ERJMPS ERROR                  ;  Go print error-msgs on error.
        HALTF%                          ;Halt program.
        JRST  GO                        ;Allow for 'continue'-command.

        ;;
        ;; ERROR: Print standardized error-message and halt.
        ;;

ERROR:  MOVEI T1,.PRIOU                 ;Print error on terminal (.PRIOU)
        MOVE  T2,[.FHSLF,,-1]           ;Own process, most recent error.
        SETZ  T3,                       ;No limit on size of message.
        ERSTR%                          ;Print that error message.
          JFCL                          ;  Ignore errors from ERSTR.
          JFCL                          ;  dito.
        HALTF%                          ;Stop program.
        JRST GO                         ;Allow for continuation.

        END GO

Mathematica / Wolfram Language[edit]

stream = OpenRead["file.txt"];
While[a != EndOfFile, Read[stream, Word]];
Close[stream]

MAXScript[edit]

this function will read a file line by line.

fn ReadAFile FileName = 
(	
	local in_file = openfile FileName
	while not eof in_file do
	(
		--Do stuff in here--
		print (readline in_file)
	)
	close in_file
)

Mercury[edit]

:- module input_loop.
:- interface.

:- import_module io.
:- pred main(io::di, io::uo) is det.

:- implementation.

main(!IO) :-
    io.stdin_stream(Stdin, !IO),
    io.stdout_stream(Stdout, !IO),
    read_and_print_lines(Stdin, Stdout, !IO).

:- pred read_and_print_lines(io.text_input_stream::in,
    io.text_output_stream::in, io::di, io::uo) is det.

read_and_print_lines(InFile, OutFile, !IO) :-
    io.read_line_as_string(InFile, Result, !IO),
    (
        Result = ok(Line),
        io.write_string(OutFile, Line, !IO),
        read_and_print_lines(InFile, OutFile, !IO)
    ;
        Result = eof
    ;
        Result = error(IOError),
        Msg = io.error_message(IOError),
        io.stderr_stream(Stderr, !IO),
        io.write_string(Stderr, Msg, !IO),
        io.set_exit_status(1, !IO)
    ).

mIRC Scripting Language[edit]

var %n = 1
while (%n <= $lines(input.txt)) {
  write output.txt $read(input.txt,%n)
  inc %n
}

ML/I[edit]

The very nature of ML/I is that its default behaviour is to copy from input to output until it reaches end of file.

Modula-2[edit]

PROCEDURE ReadName (VAR str : ARRAY OF CHAR);

VAR     n               : CARDINAL;
        ch, endch       : CHAR;

BEGIN
   REPEAT
      InOut.Read (ch);
      Exhausted := InOut.EOF ();
      IF  Exhausted  THEN  RETURN  END
   UNTIL  ch > ' ';             (* Eliminate whitespace         *)
   IF  ch = '['  THEN  endch := ']'  ELSE  endch := ch  END;
   n := 0;
   REPEAT
      InOut.Read (ch);
      Exhausted := InOut.EOF ();
      IF  Exhausted  THEN  RETURN  END;
      IF  n <= HIGH (str)  THEN  str [n] := ch  ELSE  ch := endch  END;
      INC (n)
   UNTIL ch = endch;
   IF  n <= HIGH (str)  THEN  str [n-1] := 0C  END;
   lastCh := ch
END ReadName;

Modula-3[edit]

MODULE Output EXPORTS Main;

IMPORT Rd, Wr, Stdio;

VAR buf: TEXT;

<*FATAL ANY*>

BEGIN
  WHILE NOT Rd.EOF(Stdio.stdin) DO
    buf := Rd.GetLine(Stdio.stdin);
    Wr.PutText(Stdio.stdout, buf);
  END;
END Output.

NetRexx[edit]

Using NetRexx ASK Special Variable[edit]

/* NetRexx */
options replace format comments java crossref symbols nobinary

-- Read from default input stream (console) until end of data
lines = ''
lines[0] = 0
lineNo = 0

loop label ioloop forever
  inLine = ask
  if inLine =  null  then leave ioloop -- stop on EOF (Try Ctrl-D on UNIX-like systems or Ctrl-Z on Windows)
  lineNo = lineNo + 1
  lines[0] = lineNo
  lines[lineNo] = inLine
  end ioloop

loop l_ = 1 to lines[0]
  say l_.right(4)':' lines[l_]
  end l_

return

Using Java Scanner[edit]

/* NetRexx */
options replace format comments java crossref symbols nobinary

-- Read from default input stream (console) until end of data
lines = ''
lines[0] = 0

inScanner = Scanner(System.in)
loop l_ = 1 while inScanner.hasNext()
  inLine = inScanner.nextLine()
  lines[0] = l_
  lines[l_] = inLine
  end l_
inScanner.close()

loop l_ = 1 to lines[0]
  say l_.right(4)':' lines[l_]
  end l_

return

Nim[edit]

Read from stdin until end of data has been reached:

var line = ""
while stdin.readLine(line):
  echo line

Choose splitting string:

import strutils

var lines = stdin.readAll()
for line in lines.split("\n"):
  echo line

Read from a known text file:

var i = open("input.txt")
for line in i.lines:
  discard # process line
i.close()

Another, shorter, way to do this:

for line in "input.text".lines:
  discard # process line

NodeJS[edit]

#!/usr/bin/env node

const EventEmitter = require('events');

function stdinLineByLine() {
  const stdin = new EventEmitter();
  let buff = '';

  process.stdin
    .on('data', data => {
      buff += data;
      lines = buff.split(/\r\n|\n/);
      buff = lines.pop();
      lines.forEach(line => stdin.emit('line', line));
    })
    .on('end', () => {
      if (buff.length > 0) stdin.emit('line', buff);
    });

  return stdin;
}

const stdin = stdinLineByLine();
stdin.on('line', console.log);

Oberon-2[edit]

Works with oo2c Version 2

MODULE InputLoop;
IMPORT
  StdChannels,
  Channel;
VAR
  reader: Channel.Reader;
  writer: Channel.Writer;
  c: CHAR;
BEGIN
  reader := StdChannels.stdin.NewReader();
  writer := StdChannels.stdout.NewWriter();
  
  reader.ReadByte(c);
  WHILE reader.res = Channel.done DO
    writer.WriteByte(c);
    reader.ReadByte(c)
  END
END InputLoop.

Execute: InputLoop < Inputloop.Mod
Output:

MODULE InputLoop;
IMPORT
  StdChannels,
  Channel;
VAR
  reader: Channel.Reader;
  writer: Channel.Writer;
  c: CHAR;
BEGIN
  reader := StdChannels.stdin.NewReader();
  writer := StdChannels.stdout.NewWriter();
  
  reader.ReadByte(c);
  WHILE reader.res = Channel.done DO
    writer.WriteByte(c);
    reader.ReadByte(c)
  END
END InputLoop.

Objeck[edit]

use IO;

bundle Default {
  class Test {
    function : Main(args : System.String[]) ~ Nil {
      f := FileReader->New("in.txt");
      if(f->IsOpen()) {
        string := f->ReadString();
        while(string->Size() > 0) {
          string->PrintLine();
          string := f->ReadString();
        };
        f->Close();
      };
    }
  }
}

OCaml[edit]

let rec read_lines ic =
  try
    let line = input_line ic in
    line :: read_lines ic
  with End_of_file ->
    []

The version above will work for small files, but it is not tail-recursive.
Below will be more scalable:

let read_line_opt ic =
  try Some (input_line ic)
  with End_of_file -> None

let read_lines ic =
  let rec loop acc =
    match read_line_opt ic with
    | Some line -> loop (line :: acc)
    | None -> (List.rev acc)
  in
  loop []
;;

Or with a higher order function:

let read_lines f ic =
  let rec loop () =
    try f (input_line ic); loop ()
    with End_of_file -> ()
  in
  loop ()

let () =
  let ic = open_in Sys.argv.(1) in
  read_lines print_endline ic

Oforth[edit]

Reads a file line by line and write each line on standard output :

: readFile(filename)   File new(filename) apply(#println) ;

Oz[edit]

%% Returns a list of lines.
%% Text: an instance of Open.text (a mixin class)
fun {ReadAll Text}
   case {Text getS($)} of false then nil
   [] Line then Line|{ReadAll Text}
   end
end

Pascal[edit]

{ for stdio }

var
 
 s : string ;

begin 
  
  repeat

    readln(s);
 
  until s = "" ;

{ for a file }

var 

 f : text ;
 s : string ;

begin

  assignfile(f,'foo');
  reset(f);
  
  while not eof(f) do
    readln(f,s);

  closefile(f);

end;

Perl[edit]

The angle brackets operator ( <...> ) reads one line at a time from a filehandle in scalar context:

open FH, "< $filename" or die "can't open file: $!";
while (my $line = <FH>) {
    chomp $line; # removes trailing newline
    # process $line
}
close FH or die "can't close file: $!";

Or you can get a list of all lines when you use it in list context:

@lines = <FH>;

Or a simpler program for lines of files entered as command line arguments or standard input:

while (<>) {
    # $_ contains a line
}

Invoking perl with the -p or -n option implies the above loop, executing its code once per input line, with the line stored in $_. -p will print $_ automatically at the end of each iteration, -n will not.

$ seq 5 | perl -pe '$_ = "Hello $_"'
Hello 1
Hello 2
Hello 3
Hello 4
Hello 5
$ seq 5 | perl -ne 'print "Hello $_"'
Hello 1
Hello 2
Hello 3
Hello 4
Hello 5

Phix[edit]

Translation of: Euphoria

Process text stream line-by-line:

without js -- (file i/o)
procedure process_line_by_line(integer fn)
    object line
    while 1 do
        line = gets(fn)
        if atom(line) then
            exit
        end if
        -- process the line
    end while
end procedure

Phixmonti[edit]

/# Rosetta Code problem: http://rosettacode.org/wiki/Input_loop
by Galileo, 10/2022 #/

include ..\Utilitys.pmt

def eof? dup -1 == enddef

"input.txt" "r" fopen
( inf 0 -1 ) for drop
    dup fgets eof? if drop exitfor else print endif
endfor
fclose


"input.txt" "r" fopen
eof? not while
    dup fgets eof? if drop false else print true endif
endwhile
fclose

PHP[edit]

$fh = fopen($filename, 'r');
if ($fh) {
    while (!feof($fh)) {
        $line = rtrim(fgets($fh)); # removes trailing newline
        # process $line
    }
    fclose($fh);
}

Or you can get an array of all the lines in the file:

$lines = file($filename);

Or you can get the entire file as a string:

$contents = file_get_contents($filename);

Picat[edit]

main =>
  Reader = open("file.txt"),
  while(not at_end_of_stream(Reader))
    L = read_line(Reader),
    println(L)
  end,
  close(Reader).


PicoLisp[edit]

This reads all lines in a file, and returns them as a list of lists

(in "file.txt"
   (make
      (until (eof)
         (link (line)) ) ) )

PL/I[edit]

declare line character (200) varying;

open file (in) title ('/TEXT.DAT,type(text),recsize(200)' );
on endfile (in) stop;

do forever;
   get file(in) edit (line) (L);
   put skip list (line);
end;

PowerShell[edit]

Get-Content c:\file.txt |
    ForEach-Object {
        $_
    }

or

ForEach-Object -inputobject (get-content c:\file.txt) {$_}

PureBasic[edit]

File objects can be read bytewise, characterwise (ASCII or UNICODE), floatwise, doublewise, integerwise, linewise ...

If OpenConsole()
  ; file based line wise
  If ReadFile(0, "Text.txt")  
    While Eof(0) = 0          
      Debug ReadString(0)      ; each line until eof
    Wend
    CloseFile(0)               
  EndIf
  
  ; file based byte wise
  If ReadFile(1, "Text.bin")  
    While Eof(1) = 0          
      Debug ReadByte(1)      ; each byte until eof
    Wend
    CloseFile(1)               
  EndIf
EndIf

Python[edit]

To create a Python3 input loop use python's `input()` function.

while(True):
      x = input("What is your age? ")
      print(x)

Python file objects can be iterated like lists:

my_file = open(filename, 'r')
try:
    for line in my_file:
        pass # process line, includes newline
finally:
    my_file.close()

One can open a new stream for read and have it automatically close when done, with a new "with" statement:

#from __future__ import with_statement  # is not needed in Python 3.6

with open(filename, 'r') as f:
    for line in f:
        pass # process line, includes newline

You can also get lines manually from a file:

line = my_file.readline() # returns a line from the file
lines = my_file.readlines() # returns a list of the rest of the lines from the file

This does not mix well with the iteration, however.


When you want to read from stdin, or (multiple) filenames are given on the command line:

import fileinput
for line in fileinput.input():
    pass # process line, includes newline

The fileinput module can also do inplace file editing, follow line counts, and the name of the current file being read etc.

R[edit]

Note that read.csv and read.table provide alternatives for files with 'dataset' style contents.

lines <- readLines("file.txt")

Racket[edit]

The following prints input lines from standard input to standard output:

#lang racket
(copy-port (current-input-port) (current-output-port))

Rapira[edit]

while 1 do
  input text: str
  output: str
od

Raku[edit]

(formerly Perl 6)

In Raku, filehandles etc. provide the .lines and .words methods which return lazy lists, and can thus they be iterated using a for loop...

Line-by-line (line endings are automatically stripped)

  • From a file:
    for "filename.txt".IO.lines -> $line {
        ...
    }
    
  • From standard input:
    for $*IN.lines -> $line {
        ...
    }
    
  • From a pipe:
    for runfind -iname *.txt», :out).out.lines -> $filename {
        ...
    }
    
  • From a pipe, with custom line separator (in this example to handle filenames containing newlines):
    for runfind -iname *.txt -print0», :nl«\0», :out).out.lines -> $filename {
        ...
    }
    

Word-by-word

  • From a file
    for "filename.txt".IO.words -> $word {
        ...
    }
    
  • From standard input or a pipe, accordingly.

REBOL[edit]

REBOL [
	Title: "Basic Input Loop"
	URL: http://rosettacode.org/wiki/Basic_input_loop
]

; Slurp the whole file in:
x: read %file.txt

; Bring the file in by lines:
x: read/lines %file.txt

; Read in first 10 lines:
x: read/lines/part %file.txt 10

; Read data a line at a time:
f: open/lines %file.txt
while [not tail? f][
	print f/1 
	f: next f ; Advance to next line.
]
close f

REXX[edit]

version 1a[edit]

Works with: oorexx and Regina

Reading line by line from the standard input using linein and lines did not work.

do while stream(stdin, "State") <> "NOTREADY"
  call charout ,charin(stdin)
end

version 1b[edit]

Works with: oorexx and Regina

Apparently only lines() does not work

Do Until input=''
  input=linein(stdin)
  Call lineout ,input
  End

version 2[edit]

Works with: ARexx
/* -- AREXX -- */
do until eof(stdin)
  l = readln(stdin)
  say l
end

version 3[edit]

Note that if REXX is reading from the default (console) input stream, there is no well-
defined e-o-f (end of file), so to speak.

Therefore, the following two REXX programs use the presence of a null line to indicate e-o-f.

/*REXX program reads from the (console) default input stream until null*/
       do  until _==''
       parse pull _                    
       end   /*until*/                 /*stick a fork in it, we're done.*/

version 4[edit]

/*REXX program reads from the (console) default input stream until null*/
       do  until _==''
       _= linein()
       end   /*until*/                 /*stick a fork in it, we're done.*/

Ring[edit]

fp = fopen("C:\Ring\ReadMe.txt","r")

r = fgetc(fp)
while isstring(r)
      r = fgetc(fp)
      if r = char(10) see nl
      else see r ok
end
fclose(fp)

Ruby[edit]

Ruby input streams are IO objects. One can use IO#each or IO#each_line to iterate lines from a stream.

stream = $stdin
stream.each do |line|
  # process line
end

IO objects are also Enumerable (like Array or Range), and have methods like Enumerable#map, which call IO#each to loop through lines from a stream.

# Create an array of lengths of every line.
ary = stream.map {|line| line.chomp.length}

To open a new stream for reading, see Read a file line by line#Ruby.

Run BASIC[edit]

open "\testFile.txt" for input as #f
while not(eof(#f))
line input #f, a$
print a$
wend
close #f

Rust[edit]

 use std::io::{self, BufReader, Read, BufRead};
use std::fs::File;

fn main() {
    print_by_line(io::stdin())
        .expect("Could not read from stdin");

    File::open("/etc/fstab")
        .and_then(print_by_line)
        .expect("Could not read from file");
}

fn print_by_line<T: Read>(reader: T) -> io::Result<()> {
    let buffer = BufReader::new(reader);
    for line in buffer.lines() {
        println!("{}", line?)
    }
    Ok(())
}

Scala[edit]

Library: Scala
Works with: Scala version 2.10.3
  scala.io.Source.fromFile("input.txt").getLines().foreach {
    line => ... }

sed[edit]

Sed by default loops over each line and executes its given script on it:

$ seq 5 | sed ''
1
2
3
4
5

The automatic printing can be suppressed with -n, and performed manually with p:

$ seq 5 | sed -n p
1
2
3
4
5

Seed7[edit]

$ include "seed7_05.s7i";
 
const proc: main is func
  local
    var string: line is "";
  begin
    while hasNext(IN) do
      readln(line);
      writeln("LINE: " <& line);
    end while;
  end func;

Sidef[edit]

To read from the standard input, you can use STDIN as your fh.

var file = File(__FILE__)
file.open_r(\var fh, \var err) || die "#{file}: #{err}"

fh.each { |line|              # iterates the lines of the fh
    line.each_word { |word|   # iterates the words of the line
        say word
    }
}

Slate[edit]

(File newNamed: 'README') reader sessionDo: [| :input | input lines do: [| :line | inform: line]].

Smalltalk[edit]

|f|
f := FileStream open: 'afile.txt' mode: FileStream read.
[ f atEnd ] whileFalse: [ (f nextLine) displayNl ] .

SNOBOL4[edit]

loop  output = input :s(loop)
end

Sparkling[edit]

var line;
while (line = getline()) != nil {
    print(line);
}

Standard ML[edit]

fun foldLines f init strm =
  case TextIO.inputLine strm of
    SOME line => foldLines f (f (line, init)) strm
  | NONE => init

Example: Output the lines from stdin in reverse order.

val () = (print o foldLines op^ "") TextIO.stdIn

Tcl[edit]

set fh [open $filename]
while {[gets $fh line] != -1} {
    # process $line
}
close $fh

For “small” files, it is often more common to do this:

set fh [open $filename]
set data [read $fh]
close $fh
foreach line [split $data \n] {
    # process line
}

TUSCRIPT[edit]

$$ MODE TUSCRIPT
file="a.txt"
ERROR/STOP OPEN (file,READ,-std-)
ACCESS source: READ/RECORDS/UTF8 $file s,text
LOOP
    READ/NEXT/EXIT source
    PRINT text
ENDLOOP
ENDACCESS source

TypeScript[edit]

#!/usr/bin/env node

import EventEmitter from 'events';

function stdinLineByLine() {
  const stdin = new EventEmitter();
  let buff = '';
  let lines;

  process.stdin
    .on('data', (data) => {
      buff += data;
      lines = buff.split(/\r\n|\n/);
      buff = lines.pop();
      lines.forEach((line) => stdin.emit('line', line));
    })
    .on('end', () => {
      if (buff.length > 0) stdin.emit('line', buff);
    });

  return stdin;
}

const stdin = stdinLineByLine();
stdin.on('line', console.log);

UNIX Shell[edit]

When there is something to do with the input, here is a loop:

while read line ; do
  # examine or do something to the text in the "line" variable
  echo "$line"
done

The following echoes standard input to standard output line-by-line until the end of the stream.

cat < /dev/stdin > /dev/stdout

Since cat defaults to reading from standard input and writing to standard output, this can be further simplified to the following.

cat

UnixPipes[edit]

the pipe 'yes XXX' produces a sequence

read by lines:

yes 'A B C D ' | while read x ; do echo -$x- ; done

read by words:

yes 'A B C D ' | while read -d\  a ; do echo -$a- ; done

Ursa[edit]

decl file f
f.open "filename.txt"
while (f.hasnext)
	out (in string f) endl console
end while

Vala[edit]

int main() {
        string? s;
        while((s = stdin.read_line()) != null) {
                stdout.printf("%s\n", s);
        }
        return 0;
}

VBA[edit]

Public Sub test()
    Dim filesystem As Object, stream As Object, line As String
    Set filesystem = CreateObject("Scripting.FileSystemObject")
    Set stream = filesystem.OpenTextFile("D:\test.txt")
    Do While stream.AtEndOfStream <> True
        line = stream.ReadLine
        Debug.Print line
    Loop
    stream.Close
End Sub

VBScript[edit]

filepath = "SPECIFY PATH TO TEXT FILE HERE"

Set objFSO = CreateObject("Scripting.FileSystemObject")
Set objInFile = objFSO.OpenTextFile(filepath,1,False,0)

Do Until objInFile.AtEndOfStream
	line = objInFile.ReadLine
	WScript.StdOut.WriteLine line
Loop

objInFile.Close
Set objFSO = Nothing

Visual Basic .NET[edit]

This reads a stream line by line, outputing each line to the screen.

Sub Consume(ByVal stream As IO.StreamReader)
    Dim line = stream.ReadLine
    Do Until line Is Nothing
        Console.WriteLine(line)
        line = stream.ReadLine
    Loop
End Sub

Wren[edit]

import "io" for File

File.open("input.txt") { |file|
    var offset = 0
    var line = ""
    while(true) {
        var b = file.readBytes(1, offset)
        offset = offset + 1
        if (b == "\n") {
            // process 'line'
            line = "" // reset line variable
        } else if (b == "\r") { // Windows
            // wait for following "\n"
        } else if (b == "") { // end of stream
            return
        } else {
            line = line + b
        }
    }
}

x86 Assembly[edit]

GAS, 64 bit (Linux): Compiled with gcc -nostdlib. Memory maps the file and outputs one line at a time. Try ./a.out file, ./a.out < file, or ./a.out <<< "Heredoc". It's a little like cat, but less functional.

#define SYS_WRITE   $1
#define SYS_OPEN    $2
#define SYS_CLOSE   $3
#define SYS_FSTAT   $5
#define SYS_MMAP    $9
#define SYS_MUNMAP  $11
#define SYS_EXIT    $60

// From experiments:
#define FSIZEOFF    48
#define STATSIZE    144

// From Linux source:
#define RDONLY      $00     
#define PROT_READ   $0x1
#define MAP_PRIVATE $0x02
#define STDIN       $0
#define STDOUT      $1

.global _start
.text

/* Details: */
/* 
    Remember:  %rax(%rdi, %rsi, %rdx, %r10, %r8, %r9)
    - Open a file (get its fd)
        - int fd = open("filename", RDONLY)
    - Get its filesize:
        - fstat(fd, statstruct). 0 if ok. fsize at statstruct+48
    - Then memory map it.
        - void* vmemptr = mmap(vmemptr, fsize, PROT_READ, MAP_PRIVATE, fd, 0)
    - Scan for newlines, print line.
        - Keep going until done. Details at 11.
    - Unmap memory
        - munmap(vmemptr, filesize). 0 if ok.
    - Exit
 */
    
.macro ERRCHECK code
    cmpq    $\code, %rax
    je      fs_error
.endm
    
/* Local stack notes: 
    0: int fd
    4: void* vmemptr
    12: void* head
    20: void* lookahead
    28: void* end
*/
_start:
    // Open:
    movq    RDONLY, %rsi
    // Filename ptr is on stack currently as argv[1]:
    cmpq    $1, (%rsp)          // if argc is 1, default to stdin
    jnz     open_file
    subq    $36, %rsp           // local stack
    movl    STDIN, (%rsp)
    jmp     fstat
    
    open_file:
    movq    16(%rsp), %rdi      // argc(8), argv0(8) => rsp+16. filename
    movq    SYS_OPEN, %rax
    syscall
    ERRCHECK    -1
    subq    $36, %rsp           // local stack
    movl    %eax, (%rsp)        // int fd = open(argv[1], RDONLY)
    
    // fstat to get filesize
    fstat:
    movq    $statstruct, %rsi
    movl    (%rsp), %edi        // fd
    movq    SYS_FSTAT, %rax
    syscall                     // fstat(fd, statstruct)
    ERRCHECK    -1
    
    // mmap - don't forget to munmap.
    mmap:
    movq    $0, %r9             // offset
    movq    (%rsp), %r8         // fd
    movq    MAP_PRIVATE, %r10
    movq    PROT_READ, %rdx
    movq    filesize, %rsi
    movq    (%rsp), %rdi        // vmemptr
    movq    SYS_MMAP, %rax
    syscall
    ERRCHECK    -1
    movq    %rax, 4(%rsp)       // void* vmemptr = mmap(vmemptr, fsize, PROT_READ, MAP_PRIVATE, fd, 0)
    
    /* Print lines */ 
    movq    %rax, 12(%rsp)  // head = vmemptr
    addq    filesize, %rax
    decq    %rax
    movq    %rax, 28(%rsp)  // end = vmemptr+filesize-1
    scan_outer:
        movq    12(%rsp), %rax
        cmpq    28(%rsp), %rax
        jge     cleanup         // if head >= end, done
        movq    %rax, %rbx      // Using rbx as lookahead
        scan_inner:
            cmpq    28(%rsp), %rbx
            jge     writeline       // if lookahead >= end, write the line.
            cmpb    $'\n, (%rbx)
            jz      writeline       // if '\n'==*lookahead, write the line
            incq    %rbx
            jmp     scan_inner
        writeline:
            // write:
            incq    %rbx
            movq    %rbx, %rdx
            subq    12(%rsp), %rdx  // rdx <- lookahead-head
            movq    12(%rsp), %rsi
            movq    STDOUT, %rdi
            movq    SYS_WRITE, %rax
            syscall                 // write(stdout, head, lookahead-head)
            safety:
            movq    %rbx, 12(%rsp)  // head = lookahead.
            jmp     scan_outer
    
    cleanup:
    // munmap
    movq    filesize, %rsi
    movq    4(%rsp), %rdi
    movq    SYS_MUNMAP, %rax
    syscall                     // munmap(vmemptr, filesize)
    cmpq    $-1, %rax
    je      fs_error
    // close
    movl    (%rsp), %edi
    movq    SYS_CLOSE, %rax
    syscall                     // close(fd)
    ERRCHECK    -1

exit:
    movq    SYS_EXIT, %rax
    xorq    %rdi, %rdi              // The exit code.
    syscall
    
fs_error:
    movq    SYS_EXIT, %rax
    movq    $-1, %rdi
    syscall                         // exit(-1)

.data
statstruct:     // This struct is 144 bytes. Only want size (+48)
    .zero FSIZEOFF
    filesize:  // 8 bytes.
    .quad   0
    .zero   STATSIZE-FSIZEOFF+8

XPL0[edit]

Text stream is a file redirected on command line i.e: <file.txt

int C;
[repeat                                 \read file
        repeat                          \read line
                repeat  C:= ChIn(1);    \read word
                        ChOut(0, C);
                until   (C<^A ! C>^z) & (C<^0 ! C>^9);  \non-alphanumeric
        until   C < $20;                \CR, LF, or EOF
until   C = \EOF\ $1A;
]

zkl[edit]

Many objects support "stream of" concepts such as lines, characters, chunks. Some are File, Data (bit bucket), List, Console. Word by word isn't explicitly supported. If an object is stream-able, it supports methods like foreach, pump, apply, reduce, etc.

foreach line in (File("foo.txt")){...}
List(1,2,3).readln() // here, a "line" is a list element
Utils.Helpers.zipWith(False, // enumerate a file
   fcn(n,line){"%3d: %s".fmt(n,line).print()},[1..],File("cmp.zkl"))