Wait command in Linux explained with examples

1. What is the wait command in Linux?
2. What does the wait command do?
3. What is wait function in Unix?
4. What is difference between wait and sleep command in Linux?
5. How do you kill a command in Linux?
6. How do you sleep in a shell script?
7. How do you wait in command prompt?
8. How do I run a bash script?
9. What is the use of sleep command in Linux?
10. What is exec () system call?
11. What is difference between wait and Waitpid?
12. What is Pid_t?

What is the wait command in Linux?

wait is a built-in command of Linux that waits for completing any running process. wait command is used with a particular process id or job id. When multiple processes are running in the shell then only the process id of the last command will be known by the current shell.

What does the wait command do?

The wait command returns the exit status of the last command waited for. When multiple processes are given, the command waits for all processes to complete. When invoked with the -n option, the command waits only for a single job from the given pids or jobspecs to complete and returns its exit status.

What is wait function in Unix?

The wait() system call suspends execution of the current process until one of its children terminates. The call wait(&status) is equivalent to: waitpid(-1, &status, 0); The waitpid() system call suspends execution of the current process until a child specified by pid argument has changed state.

What is difference between wait and sleep command in Linux?

wait waits for a process to finish; sleep sleeps for a certain amount of seconds. wait is a BASH built-in command. ... sleep is not a shell built-in command. It is a utility that delays for a specified amount of time.

How do you kill a command in Linux?

The syntax of the kill command takes the following form: kill [OPTIONS] [PID]... The kill command sends a signal to specified processes or process groups, causing them to act according to the signal.
...
kill Command

1. 1 ( HUP ) - Reload a process.
2. 9 ( KILL ) - Kill a process.
3. 15 ( TERM ) - Gracefully stop a process.

How do you sleep in a shell script?

/bin/sleep is Linux or Unix command to delay for a specified amount of time. You can suspend the calling shell script for a specified time. For example, pause for 10 seconds or stop execution for 2 mintues. In other words, the sleep command pauses the execution on the next shell command for a given time.

How do you wait in command prompt?

You can use timeout command to wait for command prompt or batch script for the specified amount of time. The time is defined in Seconds. The above commands will break the timeout process on pressing any key. You can use /NOBREAK ignore key presses and wait for the specified time.

How do I run a bash script?

Make a Bash Script Executable

1. 1) Create a new text file with a . sh extension. ...
2. 2) Add #!/bin/bash to the top of it. This is necessary for the “make it executable” part.
3. 3) Add lines that you'd normally type at the command line. ...
4. 4) At the command line, run chmod u+x YourScriptFileName.sh. ...
5. 5) Run it whenever you need!

What is the use of sleep command in Linux?

sleep command is used to create a dummy job. A dummy job helps in delaying the execution. It takes time in seconds by default but a small suffix(s, m, h, d) can be added at the end to convert it into any other format. This command pauses the execution for an amount of time which is defined by NUMBER.

What is exec () system call?

The exec system call is used to execute a file which is residing in an active process. When exec is called the previous executable file is replaced and new file is executed. More precisely, we can say that using exec system call will replace the old file or program from the process with a new file or program.

What is difference between wait and Waitpid?

The wait function can block the caller until a child process terminates, whereas waitpid has an option that prevents it from blocking. The waitpid function doesn't wait for the child that terminates first; it has a number of options that control which process it waits for.

What is Pid_t?

pid_t data type stands for process identification and it is used to represent process ids. Whenever, we want to declare a variable that is going to be deal with the process ids we can use pid_t data type. The type of pid_t data is a signed integer type (signed int or we can say int).