How can I use a Bash array as input to a command?

Question

Say, for example, I have the following array:

files=( "foo" "bar" "baz fizzle" )

I want to pipe the contents of this array through a command, say sort, as though each element where a line in a file. Sure, I could write the array to a temporary file, then use the temporary file as input to sort, but I'd like to avoid using a temporary file if possible.

If "bar fizzle" didn't have that space character, I could do something like this:

echo ${files[@]} | tr ' ' '\012' | sort

Any ideas? Thanks!

Ignacio Vazquez-Abrams · Accepted Answer · 2011-03-31 18:20:57Z

11

sort <(for f in "${files[@]}" ; do echo "$f" ; done)

answered Mar 31, 2011 at 18:20

Ignacio Vazquez-Abrams

804k160 gold badges1.4k silver badges1.4k bronze badges

Sign up to request clarification or add additional context in comments.

3 Comments

splicer Over a year ago

Perfect! I didn't know about the <() syntax. Thanks Ignacio!

splicer Over a year ago

I also didn't know (until now) that "${files[@]}" expands to "foo" "bar" "baz fizzle" rather than "foo bar baz fizzle".

qodeninja Over a year ago

What is this particular method called?

Gordon Davisson · Accepted Answer · 2011-03-31 22:55:45Z

7

Yet another solution:

printf "%s\n" "${files[@]}" | sort

answered Mar 31, 2011 at 22:55

Gordon Davisson

128k16 gold badges141 silver badges168 bronze badges

2 Comments

splicer Over a year ago

Although this works, it seems to rely on poorly documented behavior of printf: the fact that, unlike in the C version of printf, the printf command line utility loops over the format string until there are no more arguments. If you look at the man page for printf(1) under Mac OS X, it talks about this in the BUGS section. I'll still give you the vote though ;)

Gordon Davisson Over a year ago

@splicer: I think the note in the BUGS section is talking about something else; the main DESCRIPTION section says "The format string is reused as often as necessary to satisfy the arguments." The bash(1) man page has a similar note on its printf builtin.

Tomasz Elendt · Accepted Answer · 2011-03-31 18:52:09Z

3

SAVE_IFS=$IFS
IFS=$'\n'
echo "${files[*]}" | sort
IFS=$SAVE_IFS

Of course it won't work properly if there are any newlines in array values.

answered Mar 31, 2011 at 18:52

Tomasz Elendt

1,48513 silver badges14 bronze badges

Comments

kurt · Accepted Answer · 2011-04-01 11:04:33Z

2

For sorting files I would recommend sorting in zero-terminated mode (to avoid errors in case of embedded newlines in file names or paths):

files=(
$'fileNameWithEmbeddedNewline\n.txt'
$'saneFileName.txt'
)

echo ${#files[@]}

sort <(for f in "${files[@]}" ; do printf '%s\n' "$((i+=1)): $f" ; done)
sort -z <(for f in "${files[@]}" ; do printf '%s\000' "$((i+=1)): $f" ; done) | tr '\0' '\n'

printf "%s\000" "${files[@]}" | sort -z | tr '\0' '\n'
find . -type f -print0 | sort -z | tr '\0' '\n'

sort -z reads & writes zero-terminated lines!

answered Apr 1, 2011 at 11:04

kurt

211 bronze badge

1 Comment

Walf Over a year ago

@splicer NUL-terminated is still safest for lists of data, many programs are capable of using & producing them.

Samuel Neff · Accepted Answer · 2023-05-08 19:21:37Z

1

I like to wrap common items like this into function to make it easier to understand what's going on:

pipeArray() {
    for ITEM in $@; do
        echo "$ITEM"
    done
}

DATA=('a' 'c' 'b')
pipeArray ${DATA[@]} | sort

answered May 8, 2023 at 19:21

Samuel Neff

75.3k18 gold badges144 silver badges186 bronze badges

Collectives™ on Stack Overflow

How can I use a Bash array as input to a command?

5 Answers 5

3 Comments

2 Comments

Comments

1 Comment

Comments

Your Answer

Hot Network Questions

Collectives™ on Stack Overflow

5 Answers 5

3 Comments

2 Comments

Comments

1 Comment

Comments

Your Answer

Sign up or log in

Post as a guest

Related