envsubst

substitutes environment variables in shell format strings

TLDR

Replace environment variables in stdin and output to stdout

>_ echo '[$HOME]' | envsubst
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Replace environment variables in an input file and output to stdout

>_ envsubst < [path/to/input_file]
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Replace environment variables in an input file and output to a file

>_ envsubst < [path/to/input_file] > [path/to/output_file]
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Replace environment variables in an input file from a space-separated list

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

REPORTING BUGS

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

COPYRIGHT

Copyright 2003 -2019 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 envsubst programs are properly installed at your site, the command info envsubst should give you access to the complete manual.

AUTHOR

Written by Bruno Haible.

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