Find a string pattern in a file from an NSIS script - string

Question

In an NSIS installer script, I'm trying to check if a given httpd.conf file contains the following line :
Include "c:\xxx\yyy.conf"
If so, then my installer script would not append it to the file, otherwise, it would append it.
I've come through {LineFind} but not sure this really makes what i'm trying to achieve.
What could be the simplest way to do a kind of "grep" on a text file from an NSIS script ?
Thank you !

Answer 1

Here is a sample for searching for a given line into a file, using the LogicLib for ease of syntax. The search is stopped as soon as the line is found. This sample works on the sample script itself:
# find.nsi : sample for LineFind from TextFunc.nsh
!include "textfunc.nsh"
!include "logiclib.nsh"
OutFile "find.exe"
!define lookfor `Section` ;will find
;!define lookfor `Sectionn` ;will not find
Var found
Section
StrCpy $found 0
${LineFind} "find.nsi" "/NUL" "1:-1" "GrepFunc"
${if} $found = 1
MessageBox MB_OK "string found"
${else}
MessageBox MB_OK "string NOT found"
${endIf}
SectionEnd
Function GrepFunc
${TrimNewLines} '$R9' $R9
DetailPrint "test for line $R8 `$R9`"
${if} $R9 == "${lookfor}"
StrCpy $found 1 ;set flag
Push "StopLineFind" ;stop find
${else}
Push 0 ;ignore -> continue
${endIf}
FunctionEnd