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Top Forums Shell Programming and Scripting Creating Header & Trailer for bulk volume data file Post 302420403 by Corona688 on Tuesday 11th of May 2010 01:05:30 PM
Old 05-11-2010
In general, calling cat with just one argument is a useless use of cat. Instead of running cat 3 times, just do:
Code:
cat header datafile footer > file1.txt

That's a bit more optimized than your way.

Beyond that, no; there's no UNIX system call to insert data before other data in a file, and I don't know a system that does. Nor is there a faster form of read() than the general purpose one, why would anyone ever use the "slow" one?

If whatever's using these datafiles can accept input on stdin, you could generate them at runtime to avoid the extra reads and wasted storage:
Code:
cat header datafile footer | command


Last edited by Corona688; 05-11-2010 at 02:11 PM..
 

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CAT(1)								   User Commands							    CAT(1)

NAME
cat - concatenate files and print on the standard output SYNOPSIS
cat [OPTION]... [FILE]... DESCRIPTION
Concatenate FILE(s), or standard input, to standard output. -A, --show-all equivalent to -vET -b, --number-nonblank number nonempty output lines -e equivalent to -vE -E, --show-ends display $ at end of each line -n, --number number all output lines -s, --squeeze-blank suppress repeated empty output lines -t equivalent to -vT -T, --show-tabs display TAB characters as ^I -u (ignored) -v, --show-nonprinting use ^ and M- notation, except for LFD and TAB --help display this help and exit --version output version information and exit With no FILE, or when FILE is -, read standard input. EXAMPLES
cat f - g Output f's contents, then standard input, then g's contents. cat Copy standard input to standard output. AUTHOR
Written by Torbjorn Granlund and Richard M. Stallman. REPORTING BUGS
Report cat bugs to bug-coreutils@gnu.org GNU coreutils home page: <http://www.gnu.org/software/coreutils/> General help using GNU software: <http://www.gnu.org/gethelp/> Report cat translation bugs to <http://translationproject.org/team/> COPYRIGHT
Copyright (C) 2010 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <http://gnu.org/licenses/gpl.html>. This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law. SEE ALSO
The full documentation for cat is maintained as a Texinfo manual. If the info and cat programs are properly installed at your site, the command info coreutils 'cat invocation' should give you access to the complete manual. GNU coreutils 8.5 February 2011 CAT(1)
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