Assign fields to variables - Bash

Question

Suppose I have a string with pipe separator:

str="1|2|3|4"

I want them to be assigned to specific variables.

var_a=1
var_b=2
var_c=3
var_d=4

I am doing it in this way:

var_a="`echo $str | cut -d'|' -f1`"
var_b="`echo $str | cut -d'|' -f2`"
var_c="`echo $str | cut -d'|' -f3`"
var_d="`echo $str | cut -d'|' -f4`"

Can this be done in an efficient way? Please suggest.

Would it be ok to use an array instead of five different variables? — Socowi, Jul 10 '18 at 14:18
BTW, `echo $str` is itself buggy; `echo "$str"` is slightly better (won't replace a `*` with a list of filenames, for example); `printf '%s\n' "$str"` is *much* better (works correctly with all possible values, including `-n` or `-e`, which some versions of `echo` will consume). See [BashPitfalls #14](http://mywiki.wooledge.org/BashPitfalls#echo_.24foo), and the APPLICATION USAGE section of [the POSIX `echo` specification](http://pubs.opengroup.org/onlinepubs/9699919799/utilities/echo.html). — Charles Duffy, Jul 10 '18 at 14:29

score 4 · Answer 1 · answered Jul 10 '18 at 14:18

4

It is better to use an array to store individual delimited values:

str="1|2|3|4"
IFS='|' read -ra arr <<< "$str"

#examine array values
declare -p arr

declare -a arr='([0]="1" [1]="2" [2]="3" [3]="4")'

To loop through array, use:

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

answered Jul 10 '18 at 14:18

anubhava

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That's fair assuming the OP really wants to read a completely variable number of items. I'm not sure we know that's the case, vs four specific fields having distinct meanings. – Charles Duffy Jul 10 '18 at 14:23
Yes, I just suggested an alternative assuming variable number of delimited values in input. – anubhava Jul 10 '18 at 14:25
1

Thanks. I'll use array for this purpose. – Anshuman Bhoi Jul 10 '18 at 14:36

score 3 · Answer 2 · answered Jul 10 '18 at 14:23

3

IFS='|' read -r var_a var_b var_c var_d rest <<<"$str"

rest is the variable that gets further columns after the first four, should any others exist. If you just want to discard them, the conventional name to use for a placeholder variable is _.

This is covered in detail in BashFAQ #1: How can I read a file (data stream, variable) line-by-line (and/or field-by-field)?

answered Jul 10 '18 at 14:23

Charles Duffy

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Awesome one-liner – Anshuman Bhoi Jul 10 '18 at 14:38

Assign fields to variables - Bash

2 Answers2