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Full Discussion: Script using awk to find and replace a line, how to ignore comment lines
Top Forums Shell Programming and Scripting Script using awk to find and replace a line, how to ignore comment lines Post 303039483 by MadeInGermany on Monday 7th of October 2019 05:05:42 PM
Old 10-07-2019
The RE searches require some quoting effort.
The index() function searches for plain strings and returns the position.
Also only the comments left from the search string matter.
Two reasons to go for the index() function rather than the RE.
Code:
# replace multiplier of SHMEMSIZE in sizedefs.h with $num_pages*pagesize
# generated value to substitute for current line
numpages_find_line="#define SHMEMSIZE (4096 "
numpages_replacement_line="#define SHMEMSIZE (4096 * $num_pages)"
# value of comment character for current src file, C code in this case
comment_ch1='//'
comment_ch2='/*'
# path to file we are working on
filename='./src/sizedefs.h'
# process file to switch out line to replace
awk -v find="$numpages_find_line" \
    -v replace="$numpages_replacement_line" \
    -v comment1="$comment_ch1" \
    -v comment2="$comment_ch2" \
    '
    {
      comm1pos=index($0,comment1)
      comm2pos=index($0,comment2)
      commpos=((comm1pos > 0 && comm1pos < comm2pos || comm2pos == 0 ) ? comm1pos : comm2pos)
# commpos := the leftmost comment
      findpos=index($0,find)
# unchanged if commpos is left from findpos or not found
      if (commpos > 0 && commpos < findpos || findpos == 0)
        print $0;
      else
        print replace;
    }
    ' $filename > tmp
mv tmp $filename

These 2 Users Gave Thanks to MadeInGermany For This Post:
jim mcnamara LMHmedchem
 

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LEARN ABOUT REDHAT

glookbib

LOOKBIB(1)						      General Commands Manual							LOOKBIB(1)

NAME

       lookbib - search bibliographic databases

SYNOPSIS

       lookbib [ -v ] [ -istring ] [ -tn ] filename...

       It is possible to have whitespace between a command line option and its parameter.

DESCRIPTION

       lookbib	prints a prompt on the standard error (unless the standard input is not a terminal), reads from the standard input a line contain-
       ing a set of keywords, searches the bibliographic databases filename...	for references containing those keywords,  prints  any	references
       found  on  the  standard  output,  and repeats this process until the end of input.  For each database filename to be searched, if an index
       filename.i created by indxbib(1) exists, then it will be searched instead; each index can cover multiple databases.

OPTIONS

       -v     Print the version number.

       -istring
	      When searching files for which no index exists, ignore the contents of fields whose names are in string.

       -tn    Only require the first n characters of keys to be given.	Initially n is 6.

FILES

       filename.i  Index files.

SEE ALSO

       refer(1), lkbib(1), indxbib(1)

Groff Version 1.18.1						   27 June 2001 							LOOKBIB(1)
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