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Full Discussion: Escape character - sed
Top Forums Shell Programming and Scripting Escape character - sed Post 302244406 by era on Wednesday 8th of October 2008 02:09:53 AM
Old 10-08-2008
Repeat: you need to double the backslashes if you use double quotes. This is an artefact of the shell's quoting mechanisms, not of sed syntax as such. If you use the slash as separator, you do need to backslash any slashes which are not separators; but it's better to simply use a different separator character.

Code:
sed "s%\\($name:.:[0-9]*:\\)[0-9]*:\\(.*\\):\\(/.*/.*\\):\\(/.*/.*\\)%\1$answer\2%" /etc/passwd

With single quotes, that becomes

Code:
sed 's%\('"$name"':.:[0-9]*:\)[0-9]*:\(.*\):\(/.*/.*\):\(/.*/.*\)%\1'"$answer"'\2%' /etc/passwd

The variables $name or $answer obviously cannot contain the separator character in their values (or you need to escape the values).
Last edited by era; 10-08-2008 at 03:15 AM.. Reason: Need to escape variables if they contain the separator
 

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LEARN ABOUT LINUX

shtool-subst

SHTOOL-SUBST.TMP(1)					      GNU Portable Shell Tool					       SHTOOL-SUBST.TMP(1)

NAME

       shtool-subst - GNU shtool sed(1) substitution operations

SYNOPSIS

       shtool subst [-v|--verbose] [-t|--trace] [-n|--nop] [-w|--warning] [-q|--quiet] [-s|--stealth] [-i|--interactive] [-b|--backup ext]
       [-e|--exec cmd] [-f|--file cmd-file] [file] [file ...]

DESCRIPTION

       This command applies one or more sed(1) substitution operations to stdin or any number of files.

OPTIONS

       The following command line options are available.

       -v, --verbose
	   Display some processing information.

       -t, --trace
	   Enable the output of the essential shell commands which are executed.

       -n, --nop
	   No operation mode. Actual execution of the essential shell commands which would be executed is suppressed.

       -w, --warning
	   Show warning on substitution operation resulting in no content change on every file. The default is to show a warning on substitution
	   operations resulted in no content change on all files.

       -q, --quiet
	   Suppress warning on substitution operation resulting in no content change.

       -s, --stealth
	   Stealth operation. Preserve timestamp on file.

       -i, --interactive
	   Enter interactive mode where the user has to approve each operation.

       -b, --backup ext
	   Preserve backup of original file using file name extension ext.  Default is to overwrite the original file.

       -e, --exec cmd
	   Specify sed(1) command directly.

       -f, --file cmd-file
	   Read sed(1) command from file.

EXAMPLE

	#   shell script
	shtool subst -i -e 's;(c) ([0-9]*)-2000;(c) 1-2001;' *.[ch]

	#    RPM spec-file
	%install
	    shtool subst -v -n 
		-e 's;^(prefix=).*;1 $RPM_BUILD_ROOT%{_prefix};g' 
		-e 's;^(sysconfdir=).*;1 $RPM_BUILD_ROOT%{_prefix}/etc;g' 
		`find . -name Makefile -print`
	    make install

HISTORY

       The GNU shtool subst command was originally written by Ralf S.  Engelschall <rse@engelschall.com> in 2001 for GNU shtool.  It was prompted
       by the need to have a uniform and convenient patching frontend to sed(1) operations in the OpenPKG package specifications.

SEE ALSO

       shtool(1), sed(1).

18-Jul-2008							   shtool 2.0.8 					       SHTOOL-SUBST.TMP(1)
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