ENVSUBST - substitutes environment variables in shell format strings - man - [phpMan]

Che Dong

⚡ TLDR: ENVSUBST (tldr-pages)

Substitutes environment variables with their value in shell format strings.

Replace environment variables in `stdin` and output to `stdout`
echo '{{$HOME}}' | envsubst
Replace environment variables in an input file and output to `stdout`
envsubst < {{path/to/input_file}}
Replace environment variables in an input file and output to a file
envsubst < {{path/to/input_file}} > {{path/to/output_file}}
Replace environment variables in an input file from a space-separated list
envsubst < {{path/to/input_file}} '{{$USER $SHELL $HOME}}'

ENVSUBST(1) User Commands ENVSUBST(1)

NAME
envsubst - substitutes environment variables in shell format strings

SYNOPSIS
envsubst [OPTION] [SHELL-FORMAT]

DESCRIPTION
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 en‐
vironment variables of the form $VARIABLE or ${VARIABLE} being replaced with the correspond‐
ing 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 environ‐
ment variables that are referenced in SHELL-FORMAT, one per line.

AUTHOR
Written by Bruno Haible.

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

COPYRIGHT
Copyright © 2003-2020 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.

SEE ALSO
The full documentation for envsubst is maintained as a Texinfo manual. If the info and en‐
vsubst programs are properly installed at your site, the command

info envsubst

should give you access to the complete manual.

GNU gettext-runtime 0.21 April 2024 ENVSUBST(1)

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