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18 mar 2024 · The wait command makes a shell script or terminal session wait for background processes to finish. Notably, the command works only for jobs that were launched in the current shell session. Furthermore, we can set a list of background processes that we wish to wait for.
2 lis 2023 · Linux Commands PDF. If you prefer having all the commands on a one-page reference sheet, we created a helpful Linux command line cheat sheet. You can save the list of Linux commands in PDF format by clicking the Download Linux Cheat Sheet button below.
Figure 24-1 provides an overview of how fork(), exit(), wait(), and execve() are com-monly used together. (This diagram outlines the steps taken by the shell in executing a command: the shell continuously executes a loop that reads a command, performs various processing on it, and then forks a child process to exec the command.)
To execute a command the shell normally creates a new process and waits for it to finish. A command may be run without waiting for it to finish. For example, cc pgm.c & calls the C compiler to compile the file pgm.c . The trailing & is an operator that instructs the shell not to wait for the command to finish.
Here is simple example using wait. Run some processes: $ sleep 10 & $ sleep 10 & $ sleep 20 & $ sleep 20 & Then wait for them with wait command: $ wait < <(jobs -p) Or just wait (without arguments) for all. This will wait for all jobs in the background are completed.
To execute a UNIX command, press Enter at the end of the command line. If the command is accepted, the prompt and cursor will simply appear on the next line awaiting your next command. If the command is rejected, an error message such as "Command not found" appears.
To get an overview, use “man 2 intro” in a command shell. It is also possible to invoke syscall() function directly. Each system call has a function number defined in <syscall.h> or <unistd.h>. Internally, system call is invokded by software interrupt 0x80 to transfer control to the kernel.
