fg

fg [jobspec]

fg resumes a suspended or background job, brings it into the foreground and makes it the terminal's controlling process, so it receives your keystrokes and signals again. The shell waits for the job to finish or stop before printing another prompt.Jobs reach the background either by suspending a running command with Ctrl+Z, or by starting it with a trailing &. jobs lists them with their numbers and status; fg picks one back up and bg restarts one in the background instead. With no argument, fg resumes the current job, the one marked + in the jobs output.The % prefix is a job specification, not a process ID. It is interpreted by the shell against its own job table, which is why job numbers are meaningful only inside the shell that started them.The exit status of fg is that of the resumed command, or non-zero if job control is disabled or the job does not exist.

jobspec

The job to resume. Defaults to the current job when omitted.

Job number N.

The job whose command line starts with string.

The job whose command line contains string.

The current job: the one most recently suspended or backgrounded.

The previous job.

fg requires job control, which is enabled by default in interactive shells but not in scripts. In a non-interactive shell it fails with "no job control"; set -m can enable it if the shell supports doing so.Job numbers are reused as jobs finish, so a %N that was correct a moment ago can refer to a different job later. Prefer %string in anything you type from memory.A backgrounded job keeps running and can still write to your terminal, interleaving its output with your prompt. A job stopped by Ctrl+Z is genuinely paused (SIGTSTP) and makes no progress until it is resumed.If a background job tries to read from the terminal it is stopped with SIGTTIN, showing as "stopped (tty input)"; bring it forward with fg to let it read.Jobs removed from the table with disown can no longer be reached by fg.

Job control originated in the C shell at Berkeley around 1980, and was later adopted by ksh, bash and other Bourne shell derivatives. fg is standardized by POSIX as part of the optional User Portability Utilities job control feature. It is necessarily a shell builtin, since only the shell knows its own job table.

bg(1), jobs(1), disown(1), wait(1), kill(1), nohup(1), bash(1)

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