shell variables and sed substitution Post: 302191541

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Top Forums UNIX for Advanced & Expert Users shell variables and sed substitution Post 302191541 by duderonomy on Friday 2nd of May 2008 08:29:45 PM

05-02-2008

Registered User

shell variables and sed substitution

My specific goal: automatically edit a Makefile variable's (EXTRAVERSION)
value in a kernel Makefile.

So, I have a shell script that takes one parameter, a version string:

buildkernel.sh 2.6.18.21.7-custom

In the script, I assign the parameter to K_VER:

K_VER="2.6.18.21.7-custom"

I perform string operations until I get this:
XTRA_K_VER=".21.7-custom"

I export it (thinking that the proper value would be substitued when
make was run, but the variable is not expanded):
export XTRA_K_VER

So, maybe I should forget the export?

I am using the variable, XTRA_K_VER, in a substitution in a
Makefile with the idea that the variable would be expanded:

sed -f script.sed <Makefile.old >Makefile.new

where script.sed contains the following:

s#$[[:blank:]]*EXTRAVERSION$[[:blank:]]*=[[:blank:]]*.*#\1 = $XTRA_K_VER#

The issue I am experiencing is that I want the value of XTRA_K_VER to
be used in the Makefile as opposed to the literal variable name. I do not
have a preference whether I insert the variable form of the entity (into
the Makefile) or the literal string value of the variable.

From what I have described, is there a reasonably clean way to let the
sed script expand the value of the variable before the substitution? I
thought about re-writing the sed script dynamically upon every invocation
of the program, but that seems a bit extreme to me (and potentially
challenging for others to maintain in the future).

Thanks in advance. I really appreciate the experience of the people on this site. Smilie

Cheers,
:-D

duderonomy

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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)