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Full Discussion: Replace last n lines
Top Forums Shell Programming and Scripting Replace last n lines Post 303028079 by bakunin on Sunday 30th of December 2018 07:43:01 PM
Old 12-30-2018
Quote:
Originally Posted by onenessboy
how can i do it with unix command instead of manually editing file.
You seem to want to automatically update some sort of source-code. There is a specialised utility for that, it is called patch. In general it is fed a diff-output file and applies this diff to a sourcce file. This is the common way to update the source in a source-rpm to a higher version. The update will contain all the diffs which, when applied to an older version, give you the newer version. The man page of patch is rather exhaustive, so i suggest to read it carefully. If there are still questions please do not hesitate to raise them.

If you just want to replace fixed lines with a fixed text you could create a "changes-file" that might look like this:

Code:
<line-nr>|replacement-text

i.e.
Code:
25|replacement1
27|replacement2

and feed it the following script, which just an infinitely dumb version of patch:

Code:
#! /bin/ksh

typeset    fIn="/some/input/file"
typeset    fOut="/some/output/file"
typeset    fChanges="/file/with/the/changes/as/mentioned"
typeset -i iLine=0
typeset    chLine=""
typeset    fTmp="/tmp/myscript.$$"


cp "$fIn" "$fTmp"
while IFS="|" read iLine chLine ; do
     if sed "$iLine"' s/.*/'"$chLine"'/' "$fTmp" > "$fOut" ; then
          cp  "$fOut" "$fTmp"
     else
          exit 1
     fi
done < "$fChanges"

exit 0

Notice that in this case the replacement text must not contain regexes, i.e. backreferences like \1

I hope this helps.

bakunin
Last edited by RudiC; 12-31-2018 at 06:07 AM.. Reason: "path" & "answer" typos
 

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LEARN ABOUT DEBIAN

gendiff

GENDIFF(1)						      General Commands Manual							GENDIFF(1)

NAME

       gendiff - utility to aid in error-free diff file generation

SYNOPSIS

       gendiff <directory> <diff-extension>

DESCRIPTION

       gendiff	is  a  rather  simple script which aids in generating a diff file from a single directory.  It takes a directory name and a "diff-
       extension" as its only arguments.  The diff extension should be a unique sequence of characters added to the end of all	original,  unmodi-
       fied files.  The output of the program is a diff file which may be applied with the patch program to recreate the changes.

       The  usual  sequence  of events for creating a diff is to create two identical directories, make changes in one directory, and then use the
       diff utility to create a list of differences between the two.  Using gendiff eliminates the need for the  extra,  original  and	unmodified
       directory copy.	Instead, only the individual files that are modified need to be saved.

       Before editing a file, copy the file, appending the extension you have chosen to the filename.  I.e. if you were going to edit somefile.cpp
       and have chosen the extension "fix", copy it to somefile.cpp.fix before editing it.  Then edit the first copy (somefile.cpp).

       After editing all the files you need to edit in this fashion, enter the directory one level above where your source code resides, and  then
       type

	   $ gendiff somedirectory .fix > mydiff-fix.patch

       You should redirect the output to a file (as illustrated) unless you want to see the results on stdout.

SEE ALSO

       diff(1), patch(1)

AUTHOR

       Marc Ewing <marc@redhat.com>

4th Berkeley Distribution					  Mon Jan 10 2000							GENDIFF(1)
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