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Full Discussion: sed - use back reference in 2nd command
Top Forums Shell Programming and Scripting sed - use back reference in 2nd command Post 303001663 by bakunin on Wednesday 9th of August 2017 03:17:30 AM
Old 08-09-2017
Quote:
Originally Posted by JenniferAmon
I'll look at the hold space as an option.
Here is an example on how to use the hold space. It does not exactly solve your requirement but illustrates IMHO quite well how the mechanism works:

This is your input file:

Code:
=Chapter 1
line 1
line 2
line 3
=Chapter 2
line A
line B
line C

We want the "chapter headings" to appear after every line of that chapter like this:

Code:
line 1 (Chapter 1)
line 2 (Chapter 1)
line 3 (Chapter 1)
line A (Chapter 2)
line B (Chapter 2)
line C (Chapter 2)

The following sed-script will do this. I have added comments, which are NOT part of the script, so you should remove them when you try it:

Code:
sed '/^=/ {                     # only lines starting with "=" , do:
             s/^=//             #    remove the leading equal sign
             s/^/ (/            #    add a leading " (" to the remainder
             s/$/)/             #    add a trailing ")"
             h                  #    move the result to the hold space
             d                  #    delete the line from pattern space
          }
     G                          # all lines: add content of hold space to pattern space
     s/\n// ' inputfile         # remove EOL markers from inside lines

Notice that the last line is necessary: the hold space is delimited by its own EOL marker which is copied to the pattern space too. A line in pattern space would look like:

Code:
<line content><EOL>                  # initially, after reading in the line
<line content><EOL><hold space><EOL> # after copying hold space content

and you need to get rid of the EOL in the middle so that the line when printed is not broken into two.

I hope this helps.

bakunin
 

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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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