bash loop through list of strings

Question

Is it possible to format this sample:

for i in string1 string2 stringN
do
 echo $i
done

to something similar to this:

for i in 
string1
string2
stringN
do
 echo $i
done

EDIT: Sorry for confusion, didn't realize that there was different methods of executing script - sh <scriptname> versus bash <scriptname> and also this thing which I cannot name right now - #!/bin/sh and #!/bin/bash :)

@waayee: In that case an array is your best bet. See Glenn Jackman's answer. — jesse_b, Jun 20 '18 at 18:45

score 101 · Accepted Answer · answered Jun 20 '18 at 18:29

101

Using arrays in bash can aid readability: this array syntax allows arbitrary whitespace between words.

strings=(
    string1
    string2
    "string with spaces"
    stringN
)
for i in "${strings[@]}"; do
    echo "$i"
done

answered Jun 20 '18 at 18:29

glenn jackman

85,964

2

This seems most elegant, but unfortunately gives error: Syntax error: "(" unexpected – Jun 20 '18 at 18:38
2

@waayee, then you're not running it in Bash. Remember that sh isn't necessarily Bash, and especially isn't on Debian and Ubuntu. – ilkkachu Jun 20 '18 at 18:44
1

@ilkkachu Think I get it now - must run "bash " not "sh " :) – Jun 20 '18 at 19:08
@waayee, or put a proper hashbang/shebang line and run it like an executable. Required reading: Does the shebang determine the shell which runs the script? – ilkkachu Jun 20 '18 at 19:17
@glennjackman: what does the @ do? If I wanted "${strings[@]}" to be separated by commas instead of spaces, is it easy to do that? – rrrrr Nov 16 '18 at 23:44
1

@rrrrr, your questions are probably answered here: https://stackoverflow.com/q/12314451/7552 – glenn jackman Nov 17 '18 at 01:01
Syntax error "( unexpected" – Dims May 31 '19 at 10:46
Read the other comments - that error has already been discussed. – glenn jackman May 31 '19 at 10:55

score 10 · Answer 2 · answered Jun 20 '18 at 18:16

10

You can escape the linebreak with a backslash:

$ for i in \
> hello \
> world
> do
> echo $i
> done
hello
world
$

answered Jun 20 '18 at 18:16

Andy Dalton

13,993

score 6 · Answer 3 · edited Jul 23 '19 at 09:18

6

list='a b c d'
for element in $list;do 
    echo "$element"
done

edited Jul 23 '19 at 09:18

Bart

2,221

answered Jul 23 '19 at 08:06

guest

71

You are missing semicolons! – 41754 Jul 23 '19 at 08:46
Note that this would work as long as each string is a separate word. As soon as you have spaces in your strings, the spaces would break the string apart into multiple words. Also, if the $list string contains filename globbing characters (list='* * * *'), the shell would potentially replace these with matching filenames. – Kusalananda Jul 23 '19 at 09:29

Kusalananda · Answer 4 · 2018-07-20T09:05:27.417

You may escape the newlines before/after each item that you loop over:

for i in \
    string1 \
    string2 \
    stringN
do
   printf '%s\n' "$i"
done

Or, for this simple example:

printf '%s\n' string1 string2 stringN

which has the same result.

Why do I need to place “do” in the same line as “for”?

Variation using a bash array:

strings=(
    string1
    string2
    stringN
)

printf '%s\n' "${strings[@]}"

score 2 · Answer 5 · answered Jun 20 '18 at 19:42

2

If switching to zsh is an option:

for string (
  string1
  'other string'
  etc..
) printf '%s\n' "$string"

answered Jun 20 '18 at 19:42

Stéphane Chazelas

544,893

score 1 · Answer 6 · answered Jan 28 '20 at 11:59

1

Same thing, less text:

array=(
        string{1..7}
)

for i in "${array[@]}"; do
    echo "$i"
done

answered Jan 28 '20 at 11:59

Cornelis van Ginkel

11

string1 etc. aren’t the literal values to be displayed, they’re placeholders, so this approach doesn’t work. – Stephen Kitt Jan 28 '20 at 12:59
if so, why bothering array ( … )? just do for i in string{1..7}; do echo "$i"; done; even printf '%s\n' string{1..7} – αғsнιη Jan 28 '20 at 13:12

score 1 · Answer 7 · answered Feb 17 '23 at 11:59

You can loop over a list of strings (with and without embedded spaces) as follows:

#!/usr/bin/env bash
var1="text-without-spaces"
var2="text with spaces"
for item in "${var1}" "${var2}" "more-without-spaces" "more with spaces"; do
    echo "'${item}'"
done

NB You can leave out braces around variable identifiers in the above example e.g. use $var1 instead of ${var1}.

This outputs:

'text-without-spaces'
'text with spaces'
'more-without-spaces'
'more with spaces'

score 0 · Answer 8 · edited Feb 25 '22 at 08:48

You can use the loop command, available here, like so:

$ loop 'echo "$ITEM"' --for string1,string2,string3

or, if you have the list in a file, one per line:

$ <file_list.txt loop 'echo "$ITEM"'

Beware however that it runs one sh invocation per item (to interpret that code whilst the item is stored in the ITEM environment variable), and that it currently chokes on sequences of bytes that don't form valid characters in UTF-8 (even if the locale's charmap is not UTF-8).

bash loop through list of strings

8 Answers8