Readline interface

From Rosetta Code
Readline interface is a draft programming task. It is not yet considered ready to be promoted as a complete task, for reasons that should be found in its talk page.

A readline interface is a line editing facility that provides auto completion facilities and the ability to recall previously typed lines. Build a simple application that accepts at least two commands and uses a readline style interface.

The interface should provide

  • the ability to recall previously typed commands
  • commandline editing
  • application specific commands

The application could be based on Simple database or something else.

If the language already provides a readline interface, then it should be demonstrated how build an application specific readline interface (one that only understands the applications commands) and also show how to customize the builtin readline to provide the above features and especially add application specific commands.

See also: Input loop

C[edit]

A program that does absolutely nothing. Type 'help' for help.

#include <readline/readline.h>
#include <readline/history.h>
#include <string.h>
 
int main()
{
char *s;
using_history();
while (1) {
s = readline("This be a prompt> ");
 
if (!s || !strcmp(s, "quit")) {
puts("bye.");
return 0;
}
 
if (!strcmp(s, "help"))
puts("commands: ls, cat, quit");
else if (!strcmp(s, "ls") || !strcmp(s, "cat")) {
printf("command `%s' not implemented yet.\n", s);
add_history(s);
} else
puts("Yes...?");
}
}

Kotlin[edit]

// version 1.0.6
 
var range = intArrayOf() // empty initially
val history = mutableListOf<String>()
 
fun greeting() {
ProcessBuilder("cmd", "/c", "cls").inheritIO().start().waitFor() // clears console in windows 10
println("** Welcome to the Ranger readline interface **")
println("** which performs operations on a range of integers **\n")
println("Commands available:")
println(" range [i] [j], help, show, square, cube, add [n], sub [n]")
println(" mul [n], prev, hist, quit")
println()
}
 
fun setRange(start: Int, end: Int) {
range = IntArray(end - start + 1) { it + start }
show()
}
 
fun help() {
println(" range [i] [j] - sets the current range to [i, j] and shows them")
println(" - if i > j, sets the current range to the single value [i]")
println(" help - displays help for each command")
println(" show - displays a maximum of 10 values from the current range")
println(" square - sets the current range to their squares and shows them")
println(" cube - sets the current range to their cubes and shows them")
println(" add [i] - adds [i] to the current range and shows them")
println(" sub [i] - subtracts [i] from the current range and shows them")
println(" mul [i] - multiplies the current range by [i] and shows them")
println(" prev - displays previous command entered")
println(" hist - displays a maximum of last 10 commands entered, newest first")
println(" quit - quits Ranger")
println()
println(" < items in square brackets denote integers to be supplied e.g. range 1 5 >")
println(" < right/left arrow keys can be used to scroll through previous commands >")
}
 
fun show() {
val max = if (range.size > 10) 10 else range.size
val more = range.size - max
for (i in 0 until max) println(" ${range[i]}")
if (more > 0) println(" plus $more more")
}
 
fun square() {
for (i in 0 until range.size) range[i] *= range[i]
show()
}
 
fun cube() {
for (i in 0 until range.size) range[i] *= range[i] * range[i]
show()
}
 
fun add(n: Int) {
for (i in 0 until range.size) range[i] += n
show()
}
 
fun sub(n: Int) {
for (i in 0 until range.size) range[i] -= n
show()
}
 
fun mul(n: Int) {
for (i in 0 until range.size) range[i] *= n
show()
}
 
fun prev() {
if (history.size == 0) println("- No history yet") else println("- ${history.last()}")
}
 
fun showHistory() {
val size = history.size
if (size == 0) {println("- No history yet"); return}
val max = if (size > 10) 10 else size
val more = size - max
for (i in size - 1 downTo size - max) println("- ${history[i]}")
if (more > 0) println("- plus $more more")
}
 
fun main(args: Array<String>) {
val r = Regex ("\\s+")
val rangeCommands = arrayOf("show", "square", "cube", "add", "sub", "mul")
greeting()
while (true) {
var command = readLine()!!.trim().toLowerCase()
if (command == "") continue
var i: Int = 0
var j: Int = 0
var addToHistory = true
 
if (command.startsWith("range")) {
if (command == "range") { println("- Parameters required, try again\n"); continue}
val splits = command.split(r)
if (splits.size == 3) {
try {
i = splits[1].toInt()
j = splits[2].toInt()
if (i > j) j = i
command = "range"
history.add("$command $i $j")
addToHistory = false
}
catch(ex: NumberFormatException) {
}
}
}
else if (command.startsWith("add") || command.startsWith("sub") || command.startsWith("mul")) {
if (command.length == 3) { println("- Parameter required, try again\n"); continue}
val splits2 = command.split(r)
if (splits2.size == 2) {
try {
i = splits2[1].toInt()
command = command.take(3)
history.add("$command $i")
addToHistory = false
}
catch(ex: NumberFormatException) {
}
}
}
 
if (range.size == 0 && command in rangeCommands) {
println("- Range has not yet been set\n")
if (addToHistory) history.add(command)
continue
}
 
when (command) {
"range" -> setRange(i, j)
"help" -> help()
"show" -> show()
"square" -> square()
"cube" -> cube()
"add" -> add(i)
"sub" -> sub(i)
"mul" -> mul(i)
"prev" -> prev()
"hist" -> showHistory()
"quit" -> return
else -> {addToHistory = false; println("- Invalid command, try again")}
}
 
if (addToHistory) history.add(command)
println()
}
}
Output:
**     Welcome to the Ranger readline interface     **
** which performs operations on a range of integers **

Commands available:
 range [i] [j], help, show, square, cube, add [n], sub [n]
 mul [n], prev, hist, quit

help
 range [i] [j] - sets the current range to [i, j] and shows them
               - if i > j, sets the current range to the single value [i]
 help          - displays help for each command
 show          - displays a maximum of 10 values from the current range
 square        - sets the current range to their squares and shows them
 cube          - sets the current range to their cubes and shows them
 add [i]       - adds [i] to the current range and shows them
 sub [i]       - subtracts [i] from the current range and shows them
 mul [i]       - multiplies the current range by [i] and shows them
 prev          - displays previous command entered
 hist          - displays a maximum of last 10 commands entered, newest first
 quit          - quits Ranger

 < items in square brackets denote integers to be supplied e.g. range 1 5 >
 < right/left arrow keys can be used to scroll through previous commands  >

range 1 3
  1
  2
  3

add 1
  2
  3
  4

mul 2
  4
  6
  8

sub 3
  1
  3
  5

square
  1
  9
  25

cube
  1
  729
  15625

hist
- cube
- square
- sub 3
- mul 2
- add 1
- range 1 3
- help

prev
- hist

show
  1
  729
  15625

quit

PARI/GP[edit]

gp uses readline, but it can also be used directly in PARI:

#include <stdio.h>
#include <pari/pari.h>
#include <readline/readline.h>
#include <setjmp.h>
 
jmp_buf env;
void gp_err_recover(long numerr) { longjmp(env, numerr); }
 
/* History handling (%1, %2, etc.)*/
pari_stack s_history;
GEN *history;
GEN parihist(long p)
{
if (p > 0 && p<=s_history.n)
return history[p-1];
else if (p<=0 && s_history.n+p-1>=0)
return history[s_history.n+p-1];
pari_err(talker,"History result %ld not available [%%1-%%%ld]",p,s_history.n);
return NULL; /* not reached */
}
 
int main(int argc, char **argv)
{
char *in, *out;
GEN z;
entree hist={"%",0,(void*)parihist,13,"D0,L,","last history item."};
printf("Welcome to minigp!\n");
pari_init(8000000,500000);
cb_pari_err_recover = gp_err_recover;
pari_add_function(&hist);
stack_init(&s_history,sizeof(*history),(void**)&history);
(void)setjmp(env);
while(1)
{
in = readline("? ");
if (!in) break;
if (!*in) continue;
z = gp_read_str(in);
stack_pushp(&s_history,(void*)gclone(z)); /*Add to history */
out = GENtostr(z);
printf("%%%ld = %s\n",s_history.n,out);
free(in); free(out); avma=top;
}
return 0;
}

Code thanks to Bill Allombert

Pike[edit]

watch.pike is the solution from Simple database#Pike. this solution demonstrates how to retrofit an application with a readline interface by inheriting the original and overriding specific functions.

#!/usr/bin/pike
 
inherit "watch.pike";
 
Stdio.Readline readln = Stdio.Readline();
 
void print_help()
{
write("The following commands are available: \n");
write(sort(indices(functions))*", ");
write("\n");
}
 
void watch_add()
{
 ::watch_add(db);
}
 
void watch_list()
{
 ::watch_list(db);
}
 
void do_exit()
{
exit(0);
}
 
mapping functions = ([ "add":watch_add,
"list":watch_list,
"load":watch_load,
"save":watch_save,
"help":print_help,
"quit":do_exit ]);
 
string prompt_read(string prompt)
{
return readln->read(prompt+": ");
}
 
void main()
{
Stdio.Readline.History readline_history = Stdio.Readline.History(512);
readln->enable_history(readline_history);
 
string prompt="> ";
 
 
print_help();
while(1)
{
string input=readln->read(prompt);
if(!input)
exit(0);
if(input != "")
{
if (functions[input])
functions[input]();
else
{
write("unknown command\n");
print_help();
}
}
}
}

Sample session:

pike watch_rl.pike
The following commands are available:
add, help, list, load, quit, save
> load
> list
  Rosetta Code                            2 Simple Database                (27.10.2011.)
> add
Series: Rdm asks!
Title: Balanced ternary
Episode: 1
Date watched: 1.11.2011
Add new series? [y/n]: : y
> list
  Rdm asks!                               1 Balanced ternary               (1.11.2011.)
  Rosetta Code                            2 Simple Database                (27.10.2011.)
> hello
unknown command
The following commands are available: 
add, help, list, load, quit, save
> save
> quit

Racket[edit]

Racket's has a readline interface which is not used by default due to its license. This includes the usual readline-style editing, and tab-completion for Racket bindings. It is possible to use it as a library, or as a REPL convenience (both uses described in the documentation) -- but it is better to use xrepl which provides an enhanced command-line REPL and includes the readline interaction.

REXX[edit]

This REXX programs supports a REDO (re-do) with very limited editing to keep the program simple.
It has a history (which can be interrogated) and some of the simple (MS) DOS commands.
The HELP (or ?), REDO, error checking, and abbreviations took up most of the program.
"User" commands (subroutines) are identified with a leading period (.) to make it easier to understand what's what.

/*REXX program  implements  a  simple  "readline"  shell   (modeled after a DOS shell). */
trace off /*suppress echoing of non-zero retCodes*/
signal on syntax; signal on noValue /*handle REXX program errors. */
cmdX='ATTRIB CAL CHDIR COPY DEL DIR ECHO EDIT FC FIND KEDIT LLL MEM MKDIR MORE REM REXX',
'RMDIR SET TYPE VER XCOPY' /* ◄──── the legal/known commands. */
cls= 'CLS' /*define the program to clear screen. */
@hist.= '*** command not defined. ***' /*initialize the history database. */
hist#=0 /*the number of commands in the history*/
prompt='Enter command ──or──  ? ──or── Quit' /*the default PROMPT message text. */
sw=linesize() /*some REXX don't have this BIF. */
cls /*start with a clean slate (terminal). */
redoing=0 /*flag for executing naked ReDO cmd. */
/* [↓] do it 'til the fat lady sings. */
do forever; if prompter() then iterate /*Nothing entered? Then go try again. */
select /* [↓] now then, let's rock n' roll. */
when wordpos(xxxF,cmdX)\==0 then call .cmdX
when xxxF=='EXIT' | xxxF="QUIT" then leave /*da fat lady is done singing*/
when xxxF=='HISTORY' then call .history
when xxxF=='HELP' then call .help
when xxxF=='PROMPT' then call .prompt
when xxxF=='REDO' then call .redo
otherwise call er 'unknown command:' xxx yyy
end /*select*/
end /*forever*/
 
say xxxF'ting···' /*say goodbye, 'cause it's polite to do*/
exit /*stick a fork in it, we're all done. */
/*──────────────────────────────────────────────────────────────────────────────────────*/
er: say; say; say '****error****'; say; say arg(1); say; say; return
.prompt: if yyyU\=='' then prompt=yyy; return
.cmdX: xxxF yyy; return
/*──────────────────────────────────────────────────────────────────────────────────────*/
err: say; say; say center(' error! ', max(40, linesize()%2), "*"); say
do j=1 for arg(); say arg(j); say; end; say; exit 13
/*──────────────────────────────────────────────────────────────────────────────────────*/
noValue: syntax: call err 'REXX program' condition('C') "error",,
condition('D'),'REXX source statement (line' sigl"):",sourceline(sigl)
/*──────────────────────────────────────────────────────────────────────────────────────*/
.help: cmdsH= 'ATTRIB CHDIR CLS COPY DEL DIR ECHO EDIT FC FIND MEM MKDIR MORE PRINT',
'REM RMDIR SET TREE TYPE VER XCOPY' /*these have their own help via /? */
 
cmds= '?|Help|MANual ATTRIButes CALendar CD|CHDIR|CHANGEDir COPY DELete|ERASE',
'DELete|ERASE DIR ECHO EDIT FC|FILECOMPAre FIND HISTory Kedit LLL',
'MEM MD|MKDIR|MAKEDir MORE PRINT PROMPT Quit|EXIT',
'R4 RD|RMDIR|REMOVEDir REGINA REMark Rexx REDO SET TREE Type VER'
 
say center(strip(xxx yyy),sw-1,'═'); cmds_=cmds; yyyF=unabbrev(yyy)
 
help. = 'No help is available for the' yyy "command."
help.cal = 'shows a calendar for the current month or specified month.'
help.kedit = 'KEDITs the file specified.'
help.lll = 'shows a formatted listing of files in the current directory.'
help.prompt= 'sets the PROMPT message to the specified text.'
help.quit = 'quits (exits) this program.'
help.redo = 're-does the command # specified (or the last command).'
help.rexx = 'executes the REXX program specified.'
 
if yyy=='' then do j=1 while cmds_\==''
parse var cmds_ x cmds_
say left('',sw%2) changestr('|',x," | ")
end /*j*/
else select
when wordpos(yyyF,cmdsH)\==0 then yyyF '/?'
otherwise cmd?=yyyF
if left(help.yyyF,1)\==' ' then say yyyF ' ' help.yyyF
else say help.yyyF
end /*select*/
return
/*──────────────────────────────────────────────────────────────────────────────────────*/
.history: say center('history', sw-1, '═'); w=length(hist#)
do j=1 for hist#; say right(j,w) '═══►' @hist.j; end /*j*/
return
/*──────────────────────────────────────────────────────────────────────────────────────*/
prompter: if redoing then do; redoing=0; z=hist#-1 /*special case, bare REDO. */
parse var @hist.z xxx yyy
end
else do; if prompt\=='' then do; say; say prompt; end
parse pull xxx yyy
end
 
xxxU=xxx; upper xxxU; if xxx=='' then return 1 /*No input? Then try again*/
yyyU=yyy; upper yyyU; yyyU=strip(yyyU)
hist#=hist#+1; /*bump the history counter.*/
@hist.hist#=strip(xxx yyy) /*assign to history. */
xxxF=unAbbrev(xxx) /*maybe expand abbreviation*/
return 0
/*──────────────────────────────────────────────────────────────────────────────────────*/
.redo: select
when yyyU=='' then redoing=1 /*assume they want the last cmd. */
when words(yyy)\==1 then call er 'too many args specified for' xxx
when \datatype(yyy,'W') then call er "2nd arg isn't numeric for" xxx
otherwise nop
end /*select*/
if redoing then return /*handle with kid gloves. */
yyy=yyy/1 /*normalize it: +7 7. 1e1 007 7.0*/
say 'Re-doing:' @hist.yyy
@hist.yyy
return
/*──────────────────────────────────────────────────────────────────────────────────────*/
unabbrev: procedure; arg ccc
select
when abbrev('ATTRIBUTES' , ccc, 6) then return 'ATTRIB'
when abbrev('CALENDAR' , ccc, 3) then return 'CAL'
when abbrev('CHANGEDIR' , ccc, 7) |,
ccc=='CHDIR' |,
ccc=='CD' then return 'CHDIR'
when abbrev('CLEARSCREEN', ccc, 5) then return 'CLS'
when abbrev('FILECOMPARE', ccc, 9) then return 'FC'
when abbrev('DELETE' , ccc, 3) |,
ccc=='ERASE' then return 'DEL'
when abbrev('HISTORY' , ccc, 4) then return 'HISTORY'
when abbrev('HELP' , ccc, 1) |,
abbrev('MANUAL' , ccc, 3) |,
ccc=='?' then return 'HELP'
when abbrev('MAKEDIR' , ccc, 5) |,
ccc=='MKDIR' |,
ccc=='MD' then return 'MKDIR'
when abbrev('KEDIT' , ccc, 1) then return 'KEDIT'
when abbrev('QUIT' , ccc, 1) then return 'QUIT'
when abbrev('REMARK' , ccc, 3) then return 'REM'
when abbrev('REMOVEDIR' , ccc, 7) |,
ccc=='RMDIR' |,
ccc=='RD' then return 'RMDIR'
when abbrev('REXX' , ccc, 1) then return 'REXX'
when abbrev('TYPE' , ccc, 1) then return 'TYPE'
otherwise nop
end /*select*/
return ccc
 

This REXX program makes use of   LINESIZE   REXX program (or BIF) which is used to determine the screen width (or linesize) of the terminal (console).
The   LINESIZE.REX   REXX program is included here   ──►   LINESIZE.REX.

Some older REXXes don't have a changestr BIF, so one is included here   ──►   CHANGESTR.REX.

output   showing a sample session:

Enter command   ──or──  ?  ──or──  Quit
hel
═══════════════════════════════════════════hel══════════════════════════════════
                                              ?  |  Help  |  MANual
                                              ATTRIButes
                                              CALendar
                                              CD  |  CHDIR  |  CHANGEDir
                                              COPY
                                              DELete  |  ERASE
                                              DELete  |  ERASE
                                              DIR
                                              ECHO
                                              EDIT
                                              FC  |  FILECOMPAre
                                              FIND
                                              HISTory
                                              Kedit
                                              LLL
                                              MEM
                                              MD  |  MKDIR  |  MAKEDir
                                              MORE
                                              PRINT
                                              PROMPT
                                              Quit  |  EXIT
                                              R4
                                              RD  |  RMDIR  |  REMOVEDir
                                              REGINA
                                              REMark
                                              Rexx
                                              REDO
                                              SET
                                              TREE
                                              Type
                                              VER

Enter command   ──or──  ?  ──or──  Quit
rexx $mayan 123,456,787,654,321
╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗ ╔════╗
║    ║ ║    ║ ║    ║ ║    ║ ║    ║ ║    ║ ║    ║ ║ ∙  ║ ║    ║ ║ ∙  ║ ║    ║
║ ∙∙ ║ ║    ║ ║    ║ ║    ║ ║ ∙∙ ║ ║    ║ ║    ║ ║────║ ║────║ ║────║ ║    ║
║────║ ║    ║ ║    ║ ║────║ ║────║ ║ ∙  ║ ║    ║ ║────║ ║────║ ║────║ ║    ║
║────║ ║ ∙  ║ ║ ∙∙ ║ ║────║ ║────║ ║────║ ║ ∙∙ ║ ║────║ ║────║ ║────║ ║ ∙  ║
╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝ ╚════╝

Enter command   ──or──  ?  ──or──  Quit
cal
 ┌────────────────────────────────────────────────────────────────────────────┐
 │                                                                            │
 │                                                                            │
 │                                June   2012                                 │
 │                                                                            │
 │                                                                            │
 │  Sunday     Monday     Tuesday   Wednesday  Thursday    Friday    Saturday │
 ├──────────┬──────────┬──────────┬──────────┬──────────┬──────────┬──────────┤
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │  ─  1 ─  │     2    │
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 ├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 │     3    │     4    │     5    │     6    │     7    │     8    │     9    │
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 ├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 │    10    │    11    │    12    │    13    │    14    │    15    │    16    │
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 ├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 │    17    │    18    │    19    │    20    │    21    │    22    │    23    │
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 ├──────────┼──────────┼──────────┼──────────┼──────────┼──────────┼──────────┤
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 │    24    │    25    │    26    │    27    │    28    │    29    │    30    │
 │          │          │          │          │          │          │          │
 │          │          │          │          │          │          │          │
 └──────────┴──────────┴──────────┴──────────┴──────────┴──────────┴──────────┘


Enter command   ──or──  ?  ──or──  Quit
LLL
mm/dd/yyyy hh:mm ──filesize── ─────────────────filename D:\*.*─────────────────
06/01/2012 10:36       2,322  DIV_GRID.TXT
05/13/2012 20:39       1,044  MOD_EXP.REX
05/13/2012 19:39         694  MOD_EXP.TXT
06/01/2012 02:32       1,439  RCOMBN.RX_
06/01/2012 02:24       7,181  READLINT.REX
05/29/2012 22:48          60  sub00.REX
──────────────────────12,740  <──────────────total bytes  [6 files]

Enter command   ──or──  ?  ──or──  Quit
dir
 Volume in drive D is -----D-----
 Volume Serial Number is 68D0-6356

 Directory of D:\

05/09/2012  12:40    <DIR>          Config.Msi
12/16/2005  19:54    <DIR>          Documents and Settings
01/15/2006  10:33    <DIR>          Program Files
04/14/2010  19:58    <DIR>          Recycled
12/16/2005  20:29    <DIR>          System Volume Information
01/26/2011  00:21    <DIR>          temp
12/16/2005  19:42    <DIR>          WINDOWS
01/06/2006  14:43               211 boot.ini
06/01/2012  10:36             2,322 DIV_GRID.TXT
12/16/2005  20:18                 0 IO.SYS
05/13/2012  20:39             1,044 MOD_EXP.REX
05/13/2012  19:39               694 MOD_EXP.TXT
12/16/2005  20:18                 0 MSDOS.SYS
08/04/2004  12:00            47,564 NTDETECT.COM
08/04/2004  12:00           250,032 ntldr
06/01/2012  02:32             1,439 RCOMBN.RX_
06/01/2012  02:24             7,181 READLINT.REX
05/29/2012  22:48                60 sub00.REX
              11 File(s)        310,547 bytes
               7 Dir(s)   6,793,314,304 bytes free

Enter command   ──or──  ?  ──or──  Quit
help ver
════════════════════════════════════════help ver═════════════════════════════════════════
Displays the Windows XP version.

VER

Enter command   ──or──  ?  ──or──  Quit
ver

Microsoft Windows XP [Version 5.1.2600]

Enter command   ──or──  ?  ──or──  Quit
q
QUITting...

Ruby[edit]

This application provides auto-completion for these commands: search download open help history quit url prev past.
Auto-completion is applied by pressing the tab-key.
A history of the commands is navigated by the up- and down-keys. All commands are just echoed, except "quit" which exits.
It uses the Ruby 2.3 method Hash#to_proc.

require "readline"
require "abbrev"
 
commands = %w[search download open help history quit url prev past]
Readline.completion_proc = commands.abbrev.to_proc
 
while buf = Readline.readline(">", true) # true means: keep history.
exit if buf.strip == "quit"
p buf
end