# phpman > man > envsubst(1)

> **TLDR:** 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}}'`

*Source: tldr-pages*

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[ENVSUBST(1)](https://www.chedong.com/phpMan.php/man/ENVSUBST/1/markdown)                                 User Commands                                [ENVSUBST(1)](https://www.chedong.com/phpMan.php/man/ENVSUBST/1/markdown)



## 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@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                     March 2022                                  [ENVSUBST(1)](https://www.chedong.com/phpMan.php/man/ENVSUBST/1/markdown)