Truncate a file: Difference between revisions

=={{header|XPL0}}==

Works for binary files.

<lang XPL0>int I, Size, FD;

char C, FN(80), Array;

[I:= 0; \get file name from command line

loop [C:= ChIn(8);

if C = $20 \space\ then quit;

FN(I):= C;

I:= I+1;

];

FN(I):= 0;

Size:= IntIn(8); \get number of bytes from command line

if Size = 0 then [Text(0, "Length not found (or zero)"); exit 1];

Trap(false); \disable abort on errors

FD:= FOpen(FN, 0); \open specified file for input

FSet(FD, ^i);

OpenI(3);

if GetErr then [Text(0, "File not found"); exit 1];

Array:= Reserve(0); \64MB available if no procedures are called

for I:= 0 to Size-1 do \read specified number of bytes

[Array(I):= ChIn(3);

if GetErr then [Text(0, "File is too short"); exit 1];

]; \if end of file encountered, show error

FClose(FD);

FD:= FOpen(FN, 1); \open file by same name for output

FSet(FD, ^o);

OpenO(3);

if GetErr then [Text(0, "Output error"); exit 1];

for I:= 0 to Size-1 do ChOut(3, Array(I));

Close(3);

]</lang>