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

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?

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).

You can make it a function with:

export_from() {
  # local is not a standard command but is pretty common. It's needed here
  # for this code to be re-entrant (for the case where sourced files to
  # call export_from). We still use _export_from_ prefix to namespace
  # those variables to reduce the risk of those variables being some of
  # those exported by the sourced file.
  local _export_from_ret _export_from_restore _export_from_file


  # record current state of the allexport option. Some shells (ksh93/zsh)
  # have support for local scope for options, but there's no standard
  # equivalent.
  case $- in
    (*a*) _export_from_restore=;;
    (*)   _export_from_restore='set +a';;

  for _export_from_file do
    # using the command prefix removes the "special" attribute of the "."
    # command so that it doesn't exit the shell when failing.
    command . "$_export_from_file" || _export_from_ret="$?"
  eval "$_export_from_restore"
  return "$_export_from_ret"

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 '19 at 14:01
  • 1
    What does set +a do?
    – learner
    Jun 24 '20 at 5:11
  • With set, -<char> turns it on, and +<char> turns it off. Jun 11 at 15:17
  • This was awesome, by the way. After struggling for an hour to figure out why manually exporting a bunch of variables wasn't working as expected, I simply added this flag and boom! Worked. Thanks! Jun 11 at 15:18
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
  • 4
    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
  • 8
    @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
  • 2
    The one-line version that ignore comments into your .env file source .env && export $(sed '/^#/d' .env | cut -d= -f1) Jun 15 at 13:21

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.

  • 2
    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 '19 at 22:05
  • Oops, one more caveat, though a very strong one.
    – villasv
    Nov 30 '19 at 22:07
  • 2
    Also, if you're unlucky, a line may contain filename globbing characters that would pull in filenames.
    – Kusalananda
    Nov 30 '19 at 22:11
  • I guess I'm just going to outright flag the answer as dangerous. Thanks for the warnings @Kusalananda
    – villasv
    Nov 30 '19 at 22:20
  • 1
    "xargs nothing? why does this work?" I wondered. xargs man page answered: If **utility** is omitted, echo(1) is used
    – conny
    Jan 13 at 9:07

Just do:

while read LINE; do export "$LINE"; done < ./tmp.txt
  • Did you check whether that works?
    – RalfFriedl
    Jul 1 '19 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 '19 at 8:15
  • 3
    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 '19 at 15:53
  • 1
    It worked for me.
    – mchawre
    Aug 7 '19 at 5:26

This solution will export all key=values to environment variables that are in .env file, that are not empty lines or commented (#).

File: .env



$ export $(cat .env | egrep -v "(^#.*|^$)" | xargs)
  • 1
    values of multiple words must be quoted. This only removes lines which have # as first character on line, comments starting after a value are not removed
    – X Tian
    Mar 23 at 11:40

little workaround based on one of answers:

  1. create function and place it in ~/.bashrc
function myenvs() {

    if [ -z "$1" ]; then
        echo "Usage: myenvs [import file path]";
        if [ -f "$1" ]; then
            source "$1" 2>/dev/null; export $(cat "$1" | grep "=" | grep -v "^#" | awk /./ | cut -d= -f1 | xargs)
            echo "Bad file path: $1"
  1. run $ myenvs /path/to/env/file to import envs

※ if env/file has bad lines, here are errors may be appeared when source called. I just hide it, so error handling is up on you


If you need a (basic) solution that apply an export to each line (no eval nor source) use this script:

#!/bin/bash -

exec 5<abc.env

while read -r -u 5 line ; do
    line=${line%% \#*}                        # remove line comments.
    line="${line%"${line##*[![:space:]]}"}"   # remove trailing space characters.
    [[ $line == "" ]] && continue             # avoid empty lines.
    export "$line";

exec 5>&-

echo "A=<$A> " "B=<$B> " "C=<$C> " "D=<$D>"

Assuming an abc.env file that contains:

$ cat ./abc.env
C="3 4 5"
D="7 8"     # comment added
            # empty line

the script above will print:

A=<1>  B=<2>  C=<"3 4 5">  D=<"7 8">

The exec is required to have a loop without a subshell. A while ... do ... done <file will place the while loop inside a subshell ( no export command will work).

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