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Full Discussion: How to remove comments from a bash script?
Top Forums Shell Programming and Scripting How to remove comments from a bash script? Post 302660261 by LessNux on Friday 22nd of June 2012 09:21:20 AM
Old 06-22-2012
Question How to remove comments from a bash script?
I would like to remove comments from a bash script. In addition, I would like to remove lines that consist of only white spaces, and to remove blank lines.

Code:
#!/bin/bash
perl -pe 's/ *#.*$//g' $1 | grep -v ^[[:space:]]*$ | perl -pe 's/  +/ /g' > $2
#
# $1 INFILE
# $2 OUTFILE


The above code seemed to work at first. Unfortunately, however, I found later that the above code destroys the following two special variables.

${#ARRAY[@]} the number of array elements
$# the number of shell arguments

A workaround is to replace "${#" and "$#" with words that do not appear in the input file before applying the above code.


Code:
sed 's/${#/__UNUSUALWORD1__/g ; s/$#/__UNUSUALWORD2__/g' in.txt | \
perl -pe 's/ *#.*$//g' | grep -v ^[[:space:]]*$ | perl -pe 's/  +/ /g' | \
sed 's/__UNUSUALWORD1__/${#/ ; s/__UNUSUALWORD2__/$#/' > out.txt


However, the preparatory replacement is awkward. I would like to modify 's/ *#.*$//g' so that it will not match "${#" or "$#". Does anyone know a better solution?

Bash comments always start with #. However, the problem is that bash allows some exceptions where # does not lead a comment, as shown below.

Code:
${#ARRAY[@]} the number of array elements
$# the number of shell arguments
\# escaped by a backslash.
'abcd#efgh' protected by quotes
"abcd#efgh" protected by quotes

Does anyone know how to remove comments from bash scripts without destroying the exempted #'s that do not lead comments? (In addition, I would like to remove lines that consist of only white spaces, and to remove blank lines.)

Many thanks in advance.
Last edited by methyl; 06-22-2012 at 11:33 AM.. Reason: more code tags
 

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LEARN ABOUT DEBIAN

surfraw-update-path

SURFRAW-UPDATE-PATH(1)					User Contributed Perl Documentation				    SURFRAW-UPDATE-PATH(1)

NAME

       surfraw-update-path - updates PATH in shell config files

SYNOPSIS

       surfraw-update-path [-add] [-remove] [-check] [-sys] [-all] [-help] [-shell=SHELL]

DESCRIPTION

       surfraw-update-path adds the surfraw elvi directory (/usr/lib/surfraw) to your PATH in your shell's config file.

       Currently it supports bash, sh, csh, tcsh, ash, dash, ksh, pdksh, zsh, rc, and es

       Don't forget to login again or source your login files for it to take effect.

OPTIONS

       -check
	   Checks to see if the surfraw config code is present.  This is the default.

       -add
	   Adds the surfraw config code.

       -remove
	   Removes the surfraw config code

       -sys
	   Updates the system-wide shell config instead of the user.  Must be done as root.

       -shell=SHELL
	   Selects the shell to configure. Defaults to the value of the $SHELL environment variable.

	   Currently supported shells are:

	   sh, ash, bash, dash, csh, tcsh, ksh, pdksh, zsh, rc, and es.

       -all
	   Attempts to configure the startup files for all known shells

       -help
	   Gives a usage message

RETURN VALUE

       -check returns 0 if the surfraw code is present in the file, 1 if it is not found, or 2 on error.

       All other options return 0 on success, or 2 on error.

ENVIRONMENT

       SHELL
	   Used to determine which shell to configure, if -shell is not given.

       HOME
	   Used to find users config files.

       ENV Used by posix-compliant shells to specify a startup rc file.

       ZDOTDIR
	   Used to find user config files for zsh. If not set, defaults to HOME.

SEE ALSO

       surfraw(1), sh(1), ash(1), bash(1), dash(1), csh(1), tcsh(1), ksh(1), pdksh(1), zsh(1), rc(1), es(1)

AUTHOR

       Ian Beckwith <ianb@erislabs.net>

perl v5.12.4							    2011-07-12						    SURFRAW-UPDATE-PATH(1)
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