[command-line] How to "grep" out specific line ranges of a file

There are often times I'll grep -n whatev file to find what I'm looking for. Say the output is

1234: whatev 1
5555: whatev 2
6643: whatev 3

If I want to then just extract the lines between 1234 and 5555, is there a tool to do that? For static files I have a script that does wc -l of the file and then does the math to split it out with tail & head but that doesn't work out so well with log files that are constantly being written to.

The following command will do what you asked for "extract the lines between 1234 and 5555" in someFile.

sed -n '1234,5555p' someFile

If you want lines instead of line ranges, you can do it with perl: eg. if you want to get line 1, 3 and 5 from a file, say /etc/passwd:

perl -e 'while(<>){if(++$l~~[1,3,5]){print}}' < /etc/passwd

Put this in a file and make it executable:

#!/bin/bash
start=`grep -n $1 < $3 | head -n1 | cut -d: -f1; exit ${PIPESTATUS[0]}`
if [ ${PIPESTATUS[0]} -ne 0 ]; then
    echo "couldn't find start pattern!" 1>&2
    exit 1
fi
stop=`tail -n +$start < $3 | grep -n $2 | head -n1 | cut -d: -f1; exit ${PIPESTATUS[1]}`
if [ ${PIPESTATUS[0]} -ne 0 ]; then
    echo "couldn't find end pattern!" 1>&2
    exit 1
fi

stop=$(( $stop + $start - 1))

sed "$start,$stop!d" < $3

Execute the file with arguments (NOTE that the script does not handle spaces in arguments!):

1. Starting grep pattern
2. Stopping grep pattern
3. File path

To use with your example, use arguments: 1234 5555 myfile.txt

Includes lines with starting and stopping pattern.

Line numbers are OK if you can guarantee the position of what you want. Over the years, my favorite flavor of this has been something like this:

sed "/First Line of Text/,/Last Line of Text/d" filename

which deletes all lines from the first matched line to the last match, including those lines.

Use sed -n with "p" instead of "d" to print those lines instead. Way more useful for me, as I usually don't know where those lines are.

If I understand correctly, you want to find a pattern between two line numbers. The awk one-liner could be

awk '/whatev/ && NR >= 1234 && NR <= 5555' file

You don't need to run grep followed by sed.

Perl one-liner:

perl -ne 'if (/whatev/ && $. >= 1234 && $. <= 5555') {print}' file