A common way to get context about howor whya pattern appears in a file is to view the line above the match, or the line just. For example: grep -only-matching -line-number Fedora example.txt 2:Fedora. If (rc > 0) fwrite(line, numchars, 1, stdout) For added context, use the -line-number option ( -n for short) to see the line number where the matched pattern appears in the file. Rc = pcre_exec(re, NULL, line, numchars, 0, 0, offsets, MAX_OFFSET)
#LS GREP PRESERVE NEWLINE CODE#
Downsides: new code to maintain and debug, time to re-implementing portions of grep or perl depending on the complexity of the expression or if features such as -only-matching are used. you translate every other newline into the sequence that is guaranteed not to occur in the input. If you need speed then using PCRE (or some other possibly faster regex library) from C would allow the use of both a regular expression and a check whether there is a newline. 19 ls -a /usr grep ' prs' Would select from the output of ls -a /usr (which is the list of files in /usr delimited by newline characters) the lines that start by either of the p, r or s characters.
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