Store grep output in an array

Question

I need to search a pattern in a directory and save the names of the files which contain it in an array.

Searching for pattern:

grep -HR "pattern" . | cut -d: -f1

This prints me all filenames that contain "pattern".

If I try:

targets=$(grep  -HR "pattern" . | cut -d: -f1)
length=${#targets[@]}
for ((i = 0; i != length; i++)); do
   echo "target $i: '${targets[i]}'"
done

This prints only one element that contains a string with all filnames.

output: target 0: 'file0 file1 .. fileN'

But I need:

 output: target 0: 'file0'
 output: target 1: 'file1'
 .....
 output: target N: 'fileN'

How can I achieve the result without doing a boring split operation on targets?

Other answer is a generic way to build an array by running any command and this question is specific to grep --null -HR to produce output with NUL bytes. — anubhava
– anubhava, Commented Nov 30, 2021 at 8:08

anubhava · Accepted Answer · 2023-10-31 07:04:36Z

119

Old answer (written in the year 2014) made an assumption that output filenames won't contain special characters like whitespaces or globs. Here is a safe way to read those special filenames into an array: (will work with older bash versions)

while IFS= read -rd ''; do
   targets+=("$REPLY")
done < <(grep --null -HRl "pattern" .)

# check content of array
declare -p targets

On BASH 4+ you can use readarray instead of a loop:

readarray -d '' -t targets < <(grep --null -HRl "pattern" .)

Old Answer:

You can use:

targets=($(grep -HRl "pattern" .))

Note use of (...) for array creation in BASH.

Also you can use grep -l to get only file names in grep's output (as shown in my command).

edited Oct 31, 2023 at 7:04

answered Jul 22, 2014 at 14:57

anubhava

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7 Comments

Luca Davanzo Over a year ago

spectacular! I was already taking a look at "-l" option, btw great hit. Can you explain why works adding two brackets?

anubhava Over a year ago

That is syntax of array creation in BASH. If you remove outer (..) then you are merely assigning outout of grep to a simple shell variable which won't be treated as array.

anubhava Over a year ago

If that is the possibility then use grep --null with IFS= to create array

jww Over a year ago

Does this work with Posix-ly OS'es, like some of the BSDs and Solaris? I don't see -H or -R.

anubhava Over a year ago

$REPLY is internally set by bash if no variable name is provided.

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