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exec – Call and Execute the Specified Command

The exec command is a Linux command that is used to execute a command in the current process. When exec is used, the current process is replaced with a new process that is created by executing the specified command. This means that the new process inherits the environment variables, file descriptors, and current working directory of the calling process.

Overview

The exec command is used to execute a command in the current process. The syntax for the exec command is as follows:

exec command [arguments]

The command argument specifies the command to be executed, and the optional arguments argument specifies any arguments to be passed to the command.

For example, to run the ls command using exec, you would enter the following command:

exec ls

This would replace the current process with a new process that runs the ls command.

Use Cases

  • Replacing the current shell with a new program: exec can be used to replace the current shell with a new program. For example, if you want to replace the current shell with the vi text editor, you would enter the following command: exec vi.
  • Running a command with elevated privileges: exec can be used to run a command with elevated privileges. For example, if you want to run the passwd command with elevated privileges, you would enter the following command: exec sudo passwd.
  • Running a command in the background: exec can be used to run a command in the background. For example, to run the top command in the background, you would enter the following command: exec top &.

Options

The following table lists the available options for the exec command:

Option Description
-a file_descriptor Redirect file_descriptor to the command’s standard input.
-c Clear the environment before executing the command.
-e Exit the shell if the command cannot be executed.
-l Place a dash (-) in front of the command name, which makes the shell treat the command as if it were being run by a login shell.
-n Do not read the ~/.bashrc file before executing the command.
-t Update the stty settings for the terminal before executing the command.
-u username Run the command as the specified user.

Troubleshooting Tips

  • If you receive an error message that says “command not found”, make sure that the command is installed on your system and that it is in your PATH.
  • If you receive an error message that says “permission denied”, make sure that you have permission to execute the command. You may need to run the command with elevated privileges using sudo.

Notes

  • The exec command is often used in shell scripts to replace the current shell with a new program. This can be useful for running commands that require elevated privileges or for running commands in the background.
  • When using exec to run a command with elevated privileges, it is important to be careful and only run commands that you trust. Running arbitrary commands with elevated privileges can be dangerous and can potentially harm your system.

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