The following features are standard in every shell. Note that the stop, suspend, jobs, bg and fg commands are only available on systems that support job control.
Table A.1. Common Shell Features
| Command | Meaning |
|---|---|
| > | Redirect output |
| >> | Append to file |
| < | Redirect input |
| << | "Here" document (redirect input) |
| | | Pipe output |
| & | Run process in background. |
| ; | Separate commands on same line |
| * | Match any character(s) in filename |
| ? | Match single character in filename |
| [ ] | Match any characters enclosed |
| ( ) | Execute in subshell |
| ` ` | Substitute output of enclosed command |
| " " | Partial quote (allows variable and command expansion) |
| ' ' | Full quote (no expansion) |
| \ | Quote following character |
| $var | Use value for variable |
| $$ | Process id |
| $0 | Command name |
| $n | nth argument (n from 0 to 9) |
# | Begin comment |
| bg | Background execution |
| break | Break from loop statements |
| cd | Change directories |
| continue | Resume a program loop |
| echo | Display output |
| eval | Evaluate arguments |
| exec | Execute a new shell |
| fg | Foreground execution |
| jobs | Show active jobs |
| kill | Terminate running jobs |
| newgrp | Change to a new group |
| shift | Shift positional parameters |
| stop | Suspend a background job |
| suspend | Suspend a foreground job |
| time | Time a command |
| umask | Set or list file permissions |
| unset | Erase variable or function definitions |
| wait | Wait for a background job to finish |