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Full Discussion: Cut text file in place
Top Forums Shell Programming and Scripting Cut text file in place Post 302833599 by Corona688 on Wednesday 17th of July 2013 12:26:38 PM
Old 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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CUT(1)							      General Commands Manual							    CUT(1)

NAME
cut - select out columns of a file SYNOPSIS
cut [ -b | -c] list [file...] cut -f list [-d delim] [ -s] OPTIONS
-b Cut specified bytes -c Select out specific characters -d Change the column delimiter to delim -f Select out specific fields that are separated by the -i Runs of delimiters count as one -s Suppres lines with no delimiter characters, when used EXAMPLES
cut -f 2 file # Extract field 2 cut -c 1-2,5 file # Extract character columns 1, 2, and 5 cut -c 1-5,7- file # Extract all columns except 6 DESCRIPTION
[file...]" delimiter character ( see delim)" with the -f option. Lines with no delimiters are passwd through untouched" Cut extracts one or more fields or columns from a file and writes them on standard output. If the -f flag is used, the fields are sepa- rated by a delimiter character, normally a tab, but can be changed using the -d flag. If the -c flag is used, specific columns can be specified. The list can be comma or BLANK separated. The -f and -c flags are mutually exclusive. Note: The POSIX1003.2 standard requires the option -b to cut out specific bytes in a file. It is intended for systems with multi byte characters (e.g. kanji), since MINIX uses only one byte characters, this option is equivalent to -c. For the same reason, the option -n has no effect and is not listed in this man- ual page. SEE ALSO
sed(1), awk(9). CUT(1)
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