07-17-2013
In general, 'in place' almost never is, because files do not work that way. You cannot tell a disk 'snip this line here, change that text there, and make it all line up properly'. You get to seek, overwrite, and truncate, and that's it.
And that is what you need to do here -- truncate. Figure out exactly what byte you need the file to stop at, seek to that point, then truncate the rest. What languages can you use? I'm not sure you can do this in pure shell.
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LEARN ABOUT DEBIAN
explain_truncate_or_die
explain_truncate_or_die(3) Library Functions Manual explain_truncate_or_die(3)
NAME
explain_truncate_or_die - truncate a file and report errors
SYNOPSIS
#include <libexplain/truncate.h>
void explain_truncate_or_die(const char *pathname, long long length);
DESCRIPTION
The explain_truncate_or_die function is used to call the truncate(2) system call. On failure an explanation will be printed to stderr,
obtained from explain_truncate(3), and then the process terminates by calling exit(EXIT_FAILURE).
This function is intended to be used in a fashion similar to the following example:
explain_truncate_or_die(pathname, length);
pathname
The pathname, exactly as to be passed to the truncate(2) system call.
length The length, exactly as to be passed to the truncate(2) system call.
Returns:
This function only returns on success. On failure, prints an explanation and exits.
SEE ALSO
truncate(2)
truncate a file to a specified length
explain_truncate(3)
explain truncate(2) errors
exit(2) terminate the calling process
COPYRIGHT
libexplain version 0.52
Copyright (C) 2008 Peter Miller
explain_truncate_or_die(3)