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C.1. Common features
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 C-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) |
| $* | All arguments as a simple word |
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| 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 |