What does exec do in shell script?
exec command in Linux is used to execute a command from the bash itself. This command does not create a new process it just replaces the bash with the command to be executed. If the exec command is successful, it does not return to the calling process.
What is meant by input and output redirection?
On a command line, redirection is the process of using the input/output of a file or command to use it as an input for another file. It is similar but different from pipes, as it allows reading/writing from files instead of only commands. Redirection can be done by using the operators > and >> .
How to use Exec to redirect output in Bash?
In the example animation below, we use exec to redirect all standard output to a file. We then enter some commands that should generate some output. We then use exec to redirect STDOUT to the /dev/tty to restore standard output to the terminal. This effectively stops the redirection.
How to use Exec to redirect stdout to the terminal?
We then use exec to redirect STDOUT to the /dev/tty to restore standard output to the terminal. This effectively stops the redirection. Using the cat command we can see that the file contains all the redirected output. In this article we covered the basics of the exec command.
How to redirect input into a shell script?
If you use only a single angular bracket all the content of the file will be lost. A here-document is used to redirect input into an interactive shell script or program. You can run any program within a shell script without user action by supplying the required input for the interactive program, or interactive shell script.
How to redirect output to a descriptor?
Thus only stdout is pointing at the file, because stderr is pointing to the “old” stdout. Another common use for redirecting output is redirecting only stderr. To redirect a file descriptor, we use N>, where N is a file descriptor.