17.21 lookfor: Which File Has that Word?

The following simple shell script, lookfor, uses find (17.1) to look for all files in the specified directory hierarchy that have been modified within a certain time, and it passes the resulting names to grep (27.2) to scan for a particular pattern. For example, the command:

% lookfor /work -7 tamale enchilada

would search through the entire /work filesystem and print the names of all files modified within the past week that contain the words "tamale" or "enchilada". (So, for example: if this article is stored on /work, lookfor should find it.)

The arguments to the script are the pathname of a directory hierarchy to search in ($1), a time ($2), and one or more text patterns (the other arguments). This simple but slow version will search for an (almost) unlimited number of words:

#!/bin/sh
temp=/tmp/lookfor$$
trap 'rm -f $temp; exit' 0 1 2 15
find $1 -mtime $2 -print > $temp
shift; shift
for word
do grep -i "$word" `cat $temp` /dev/null
done

That version runs grep once to search for each word. The -i option makes the search find either uppercase or lowercase letters. Using /dev/null makes sure that grep will print the filename . (13.14) Watch out: the list of filenames may get too long (9.20).

The next version is more limited but faster. It builds a regular expression for egrep (27.5) that finds all the words in one pass through the files. If you use too many words, egrep will say Regular expression too long. Your egrep may not have a -i option; you can just omit it. This version also uses xargs (9.21); though xargs has its problems (9.22).

#!/bin/sh
where="$1"
when="$2"
shift; shift
# Build egrep expression like (word1|word2|...) in $expr
for word
do
    case "$expr" in
    "") expr="($word" ;;
    *) expr="$expr|$word" ;;
    esac
done
expr="$expr)"

find $where -mtime $when -print | xargs egrep -i "$expr" /dev/null