Managing environment variables

This page details all the user-facing commands in the main mode which deal with reading and writing environment variables. The changes to the variables are applied to the environment of the shell the command was executed in.

All commands are offered through shortcuts to ease access to the core functions.

Note

These commands are only available if Envprobe has been hooked in the current shell.

Reading (get, ?)

get(VARIABLE, info=False)

Read and print the value of the environment variable VARIABLE to the standard output in the format VARIABLE=value.

Parameters

  • VARIABLE – The name of the environment variable to query.

  • info (True if -i or info is given) – Whether to print additional information.

Possible invocations

  • ep get [-i|--info] VARIABLE

  • ep ?VARIABLE

  • ep VARIABLE 1

Examples
$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin

$ ep get -i PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin

PATH=
      /usr/local/bin
      /usr/bin
      /sbin
      /bin

Type: 'path'
Priting additional information:

If -i/--info is given, additional information about the variable will be printed after the initial print of the value. This additional information includes:

1

The shorthand format ep VARIABLE for ep get VARIABLE is available only if the given variable name ("VARIABLE") is not “shadowed” by a subcommand name that is valid at the time the command is executed. E.g. if get is an environment variable defined in the shell, saying ep get will not be resolved as if the user said ep get get, but instead, it will simply call ep get without a variable name, resulting in an error. As most environment variables are named in SCREAMING_SNAKE_CASE, this should not pose an issue except in the rarest of situations.

Writing (set, !, =)

set(VARIABLE, VALUE)

Set the value of VARIABLE to the specified VALUE.

Parameters

  • VARIABLE – The name of the environment variable to set.

  • VALUE – The new value to set to.

Possible invocations

  • ep set VARIABLE VALUE

  • ep !VARIABLE VALUE

  • ep VARIABLE=VALUE

Examples
$ echo $SOME_VARIABLE
# No result, the variable is not set.

$ ep set SOME_VARIABLE MyValue

$ echo $SOME_VARIABLE
MyValue

$ which ls
/bin/ls

$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin

$ ep PATH="/tmp"

$ which ls
# No result.

Undefining (undefine, ^)

undefine(VARIABLE)

Undefine the VARIABLE.

In some cases, there can be subtle differences between a variable that is defined (but usually empty string), and variables that are not defined at all. However, in many cases, the two are equivalent.

Parameters

VARIABLE – The name of the environment variable to undefine.

Possible invocations

  • ep undefine VARIABLE

  • ep ^VARIABLE

Examples
$ echo $USER
root

$ ep undefine USER

$ echo $SOME_VARIABLE
# No result, the variable is not set.

$ echo $HOME/bin
/home/user/bin

$ ep ^HOME

$ echo $HOME/bin
/bin

Adding to arrays (add, +)

Traditionally, extending a variable such as PATH with your current working directory required executing a lengthy sequence: export PATH="$(pwd):${PATH}".

add(VARIABLE, VALUE..., position=0)

Add the given VALUE (or values, can be multiple) to the VARIABLE array. The values will be located starting at the given position index, while all subsequent elements will be shifted to the right (to higher indices).

Parameters

  • VARIABLE – The name of the environment variable to add to.

  • VALUE – The value(s) to add.

  • position (int) – The position where the added value(s) will be put to. A positive position counts from the beginning of the array, while a negative position counts from the end. 0 is the first, and -1 is the last element’s position.

Possible invocations

  • ep add [--position] VARIABLE VALUE

  • ep +VARIABLE VALUE (for position = 0)

  • ep VARIABLE+ VALUE (for position = -1)

Examples
$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin
$ fancy
fancy: command not found!

$ ep add --position 0 PATH /opt/fancy/bin
$ fancy
Fancy tool works!

$ ep PATH
PATH=/opt/fancy/bin:/usr/local/bin:/usr/bin:/sbin:/bin
Using --position to control where the values will be added to. Note the ^1 markers indicating what the individual variables’ positions are understood as.
$ ep SOME_ARRAY
SOME_ARRAY=Foo:Bar:Baz
#          ^0  ^1  ^2
#          -3^ -2^ -1^

$ ep add --position 1 SOME_ARRAY BLAH
$ ep SOME_ARRAY
SOME_ARRAY=Foo:BLAH:Bar:Baz
#          ^0  ^1   ^2  ^3
#          -4^ -3^  -2^ -1^

$ ep add --position -2 SOME_ARRAY FIZZ
$ ep SOME_ARRAY
SOME_ARRAY=Foo:BLAH:FIZZ:Bar:Baz

$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin

$ ep PATH+ /

$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin:/

Note

The add command only works with environment variables that are Array. In case Envprobe did not correctly resolve the type of the variable, you can configure it yourself.

Removing from arrays (remove, -)

remove(VARIABLE, VALUE...)

Remove all occurrences of VALUE (or values, can be multiple) from the VARIABLE array.

Parameters

  • VARIABLE – The name of the environment variable to remove from.

  • VALUE – The value(s) to remove.

Possible invocations

  • ep remove VARIABLE VALUE

  • ep -VARIABLE VALUE

Examples
$ ep PATH
PATH=/opt/fancy/bin:/usr/local/bin:/usr/bin:/sbin:/bin
$ fancy
Fancy tool works!

$ ep remove PATH /opt/fancy/bin
$ fancy
fancy: command not found!

$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin:/bin
All occurrences are removed. The following array has /bin in it 7 times.
$ ep PATH
PATH=/bin:/bin:/bin:/usr/local/bin:/bin:/usr/bin:/sbin:/bin:/bin:/bin

$ ep -PATH /bin

$ ep PATH
PATH=/usr/local/bin:/usr/bin:/sbin

Note

The remove command only works with environment variables that are Array. In case Envprobe did not correctly resolve the type of the variable, you can configure it yourself.