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set – Display or Set Shell Features and Shell Variables

The set command is used to display or set shell features and shell variables. It allows you to change the behavior of the shell and customize your environment.

Overview

The set command can be used in two ways:

  • To display the current shell settings
  • To modify the current shell settings

Displaying Shell Settings

To display the current shell settings, simply type set in the terminal and press enter. This will display a list of all the shell variables and their values.

$ set
BASH=/bin/bash
BASHOPTS=cmdhist:complete_fullquote:extquote:force_fignore:hostcomplete:interactive_comments:progcomp:promptvars:sourcepath
BASH_ALIASES=()
BASH_ARGC=()
BASH_ARGV=()
...

Modifying Shell Settings

To modify the current shell settings, you can use the set command with various options and arguments. For example, you can turn on or off certain shell options, set environment variables, and define shell functions.

Here are some examples:

  • To turn on the xtrace option, which prints each command before it is executed, use set -x.
  • To turn off the errexit option, which exits the shell if any command fails, use set +e.
  • To set the EDITOR environment variable to nano, use set EDITOR=nano.
  • To define a shell function called myfunc, use set myfunc() { echo "Hello, world!"; }.

Options

The set command has many options that allow you to customize the behavior of the shell. Here are some of the most commonly used options:

Option Description
-e Exit immediately if a command exits with a non-zero status.
-x Print each command before it is executed.
-u Treat unset variables as an error and exit immediately.
-v Print each command before it is executed, but after variable expansion.
-n Read commands but do not execute them.
-o option Enable the specified shell option.
+o option Disable the specified shell option.
-p Display the current shell variables in a format that can be reused as input.
-a Export all shell variables to the environment.
-f Disable file name generation (globbing).
-h Turn on hash table debugging.
-m Enable job control.
-t Exit after reading and executing one command.

Troubleshooting Tips

  • If you encounter errors when using the set command, make sure you are using the correct syntax and options.
  • Be careful when modifying shell settings, as it can have unintended consequences. Make sure you understand the effects of each option before using it.
  • If you are unsure about the current shell settings, use set -o to display a list of all the enabled options.

Notes

  • The set command is a powerful tool for customizing your shell environment and behavior. However, it should be used with caution, as it can have unintended consequences if used improperly.
  • To make permanent changes to your shell environment, you can add set commands to your shell startup files, such as .bashrc or .bash_profile. This will ensure that your customizations are applied every time you start a new shell session.

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