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Full Discussion: Help on cat with sed!
Top Forums Shell Programming and Scripting Help on cat with sed! Post 302338869 by kbalaji_uk on Wednesday 29th of July 2009 06:13:50 AM
Old 07-29-2009
Ok edidata to be more specific and clear cat x | sed 's/A/a/g' > x. Where x is say a file then the output in one case is empty i.e file x is now empty even the old content is gone. In another case x which had some text with 'A' has replace with 'a' and is written into file. BTW checked sed version cat version linux kernel version all are same in the box only difference is one is faster than the other in speed.
 

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LEARN ABOUT DEBIAN

cat

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, overrides -n

       -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) 2011 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

       tac(1)

       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 8.12.197-032bb					  September 2011							    CAT(1)
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