84

I have a tmp.txt file containing variables to be exported, for example:

a=123
b="hello world"
c="one more variable"

How can I export all these variables using the export command, so that they can later be used by child processes?

67
source tmp.txt
export a b c
./child ...

Judging by your other question, you don't want to hardcode the variable names:

source tmp.txt
export $(cut -d= -f1 tmp.txt)

test it:

$ source tmp.txt
$ echo "$a $b $c"
123 hello world one more variable
$ perl -E 'say "@ENV{qw(a b c)}"'

$ export $(cut -d= -f1 tmp.txt)
$ perl -E 'say "@ENV{qw(a b c)}"'
123 hello world one more variable
  • 2
    This won't work if the environment file contains comments, for example. (eg. files that can be reused by systemd's EnvironmentFile) – Chris Lamb Nov 12 '17 at 22:36
  • 3
    @ChrisLamb you can use grep to skip comments: export $(grep --regexp ^[A-Z] tmp.txt | cut -d= -f1) – gvee Jul 2 '18 at 16:05
186
set -a
. ./tmp.txt
set +a

set -a causes variables¹ defined from now on to be automatically exported. It's available in any Bourne-like shell. . is the standard and Bourne name for the source command so I prefer it for portability (source comes from csh and is now available in most modern Bourne-like shells including bash though (sometimes with a slightly different behaviour)).

In POSIX shells, you can also use set -o allexport as a more descriptive alternative way to write it (set +o allexport to unset).


¹ In bash, beware that it also causes all functions declared while allexport is on to be exported to the environment (as BASH_FUNC_myfunction%% environment variables that are then imported by all bash shells run in that environment, even when running as sh).

  • if variable's value has blank, the second run will failed – jk2K Nov 25 at 14:01
1

Just do:

while read LINE; do export "$LINE"; done < ./tmp.txt
  • Did you check whether that works? – RalfFriedl Jul 1 at 20:33
  • @RalfFriedl this should work, why not? It's not very elegant and sourcing with set -a would be far simpler, but this does actually work. – terdon Jul 2 at 8:15
  • This is brittle. It does not allow comments in the input file, does not handle quoted variable values properly, and fails on multi-line variables. Granted I don't have many multi-line variables, but I do use comments regularly and often need to use quotes for variable values. – Louis Jul 24 at 15:53
  • It worked for me. – mchawre Aug 7 at 5:26
0

A dangerous one-liner that doesn't require source:

export $(xargs <file)
  • It can't handle comments, frequently used in environment files
  • It can't handle values with whitespace, like in the question example
  • It may unintentionally expand glob patterns into files if they match by any chance

It's a bit dangerous because it passes the lines through bash expansion, but it has been useful to me when I know I have safe environment files.

  • 1
    You should try that on the example given in the question. You will notice that you get the wrong values due to the splitting that the shell does on whitespaces. – Kusalananda Nov 30 at 22:05
  • Oops, one more caveat, though a very strong one. – villasv Nov 30 at 22:07
  • 1
    Also, if you're unlucky, a line may contain filename globbing characters that would pull in filenames. – Kusalananda Nov 30 at 22:11
  • I guess I'm just going to outright flag the answer as dangerous. Thanks for the warnings @Kusalananda – villasv Nov 30 at 22:20

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