envsubst

Replace environment variables in stdin and output to stdout

$ echo '[$HOME]' | envsubst

$ envsubst < [path/to/input_file]

$ envsubst < [path/to/input_file] > [path/to/output_file]

$ envsubst '[$USER $SHELL $HOME]' < [path/to/input_file]

envsubst [OPTION] [SHELL-FORMAT]

Substitutes the values of environment variables.

Operation mode:

-v, --variables

output the variables occurring in SHELL-FORMAT

Informative output:

-h, --help

display this help and exit

-V, --version

output version information and exit

In normal operation mode, standard input is copied to standard output, with references to environment variables of the form $VARIABLE or ${VARIABLE} being replaced with the corresponding values. If a SHELL-FORMAT is given, only those environment variables that are referenced in SHELL-FORMAT are substituted; otherwise all environment variables references occurring in standard input are substituted.

When --variables is used, standard input is ignored, and the output consists of the environment variables that are referenced in SHELL-FORMAT, one per line.

Report bugs in the bug tracker at <https://savannah.gnu.org/projects/gettext> or by email to <bug-gettext@gnu.org>.

Copyright © 2003-2023 Free Software Foundation, Inc. License GPLv3+: GNU GPL version 3 or later <https://gnu.org/licenses/gpl.html>
This is free software: you are free to change and redistribute it. There is NO WARRANTY, to the extent permitted by law.

The full documentation for envsubst is maintained as a Texinfo manual. If the info and envsubst programs are properly installed at your site, the command info envsubst should give you access to the complete manual.

Written by Bruno Haible.