Extract range of lines in a file encompassing pattern match

interval.sh

#!/bin/sh

# grep-interval -- extract range of lines including the first
# line matching the specified pattern, the last line matching
# the pattern, and all lines in between.

if (( $# != 2 )) ; then
    echo "Usage: $0 pattern file" 1>&2
    exit 1
fi

pattern=$1
file=$2

first=$(grep -n "$pattern" "$file"|head -1|cut -d: -f1)
[[ -z $first ]] && exit 0

last=$(grep -n "$pattern" "$file"|tail -1|cut -d: -f1)

tail -n +$((first)) "$file" |head -$((last-first+1))

Very useful for extracting lines from a log when you want to follow everything happening with respect an event, but there may be intermediate lines of interest that won't be caught with grep.