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Full Discussion: sed pattern matching question
Top Forums Shell Programming and Scripting sed pattern matching question Post 302518175 by topmhat on Thursday 28th of April 2011 08:09:13 PM
Old 04-28-2011
Thank you both. I too feel the ABCD is literal. I think mirni is correct about the overall behavior (as were you ddreggors with the exception of the print).

The twist in all of this is that this sed command has been used at the end of an extraction process, supposedly to remove lines that contain leading ABDC followed by a pipe, and trailing ABCD preceded by a pipe. And to print (p), everything else to a .tmp file. Then a mv command was usedto overwrite the original file with the tmp file.

But when I run this command against a sample file created with the first 1000 lines of one of our prod files, the tmp file is empty each time. However when it runs in production the original file has the same byte count as the processed and renamed output file (as measured before the mv command is carried out). So print is working in prod.

The files are too big to diff though I compared the first 100K rows of the before and after to each other, and then the last 100K rows and came up with no differences each time. So in production it is writing every line to the tmp file, but when I run it it writes no lines to the tmp file.

My original intent was to change this over to a Perl pattern match and replace in the hopes of speeding up the process, but I wanted to understand the sed statement first. Now it's looking like at best sed is doing nothing, given that the before and after files are identical. But I still need to figure out why my tmp file is empty, using the same command (from the command line), while it prod the tmp file is the same size as the original file (when run from a script).
 

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LEARN ABOUT DEBIAN

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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