What does ampersand mean in bash?
A single ampersand ends an asynchronous command. That means Bash will run it in the background and run the next command immediately after, without waiting for the first one to finish. Only the command before & is executed asynchronously and you must not put a ; after &, & replaces ;.
Table of Contents
What does & do in bash?
The & makes the command run in the background. From man bash: If the control operator & terminates a command, the shell executes the command in the background in a subshell. The shell does not wait for the command to complete and the return status is 0.
What does ampersand mean at the end of a shell script line?
Single Ampersand This trailing ampersand tells the shell to run the command in the background, that is, it forks and runs in a separate subshell, as a job, asynchronously. A single ampersand & can also delimit a list of commands to be executed asynchronously.
What is & at the end of the command?
What is the & terminator? If a command is terminated by the control operator ( ‘&’ ), the shell will execute the command asynchronously in a subshell. This means that the shell will not wait for the command to finish before executing the next command.
What symbol is used for the end of the command?
In ASCII and Unicode, the character is encoded as U+0004. May be referred to as Ctrl + D , ^D in caret notation.
What is the use of nohup?
Nohup is a command used to run a process (job) on a server and have it continue after it has logged off or lost connection to the server. Nohup is more suitable for long work runs.
Why do we need nohup?
When running large data imports on a remote host, for example, you might want to use nohup to ensure that disconnection won’t force you to start over when you reconnect. It’s also used when a developer doesn’t properly demonize a service, so you should use nohup to make sure it doesn’t get killed when you log out.
What does an ampersand do on the Bash command line?
To do this, just add an ampersand to the command line: Bash shows you the ID of the process that was started, and then returns you to the command line. You can then continue using your terminal window. Many Linux commands accept a file as a parameter and take their data from that file.
What does ampersand mean at the end of a shell line?
On the first line you will probably find one of: or similar. In basic terms, the command after #! (such as /bin/sh) is executed and the contents of the rest of the script file are fed in one line at a time. Note that the file must also be made executable with chmod so that you can run it as a command.
When to use ampersand or & in nohup?
This is almost always used with nohup because you normally want to exit the shell after starting the command. Using the ampersand (&) will execute the command in a child process (child of the current bash session).
Can a single ampersand delimit a list of commands?
A single ampersand & can also delimit a list of commands to be executed asynchronously. In this example, all 3 python scripts are running at the same time, in separate subshells. Your stdout will still be attached to the main shell, so if you run this from a Linux terminal, you’ll still see the results.