Bash Builtin Commands 內建指令

Linux啟動之後所進入的通常就是Bash，面對這個Command-line Interface我們使用者應該如何操作！黑黑的畫面上閃爍著輸入游標，到底有什麼指令可以使用？請求協助輸入help是一個方法，但這只會列出Bash內建的所有指令

列出Bash內建的所有指令與敘述：help -d '*'

1. % - Resume job in foreground.
2. (( ... )) - Evaluate arithmetic expression.
3. . - Execute commands from a file in the current shell.
4. : - Null command.
5. [ - Evaluate conditional expression.
6. [[ ... ]] - Execute conditional command.
7. alias - Define or display aliases.
8. bg - Move jobs to the background.
9. bind - Set Readline key bindings and variables.
10. break - Exit for, while, or until loops.
11. builtin - Execute shell builtins.
12. caller - Return the context of the current subroutine call.
13. case - Execute commands based on pattern matching.
14. cd - Change the shell working directory.
15. command - Execute a simple command or display information about commands.
16. compgen - Display possible completions depending on the options.
17. complete - Specify how arguments are to be completed by Readline.
18. compopt - Modify or display completion options.
19. continue - Resume for, while, or until loops.
20. coproc - Create a coprocess named NAME.
21. declare - Set variable values and attributes.
22. dirs - Display directory stack.
23. disown - Remove jobs from current shell.
24. echo - Write arguments to the standard output.
25. enable - Enable and disable shell builtins.
26. eval - Execute arguments as a shell command.
27. exec - Replace the shell with the given command.
28. exit - Exit the shell.
29. export - Set export attribute for shell variables.
30. false - Return an unsuccessful result.
31. fc - Display or execute commands from the history list.
32. fg - Move job to the foreground.
33. for - Execute commands for each member in a list.
34. for (( - Arithmetic for loop.
35. function - Define shell function.
36. getopts - Parse option arguments.
37. hash - Remember or display program locations.
38. help - Display information about builtin commands.
39. history - Display or manipulate the history list.
40. if - Execute commands based on conditional.
41. jobs - Display status of jobs.
42. kill - Send a signal to a job.
43. let - Evaluate arithmetic expressions.
44. local - Define local variables.
45. logout - Exit a login shell.
46. mapfile - Read lines from the standard input into an indexed array variable.
47. popd - Remove directories from stack.
48. printf - Formats and prints ARGUMENTS under control of the FORMAT.
49. pushd - Add directories to stack.
50. pwd - Print the name of the current working directory.
51. read - Read a line from the standard input and split it into fields.
52. readarray - Read lines from a file into an array variable.
53. readonly - Mark shell variables as unchangeable.
54. return - Return from a shell function.
55. select - Select words from a list and execute commands.
56. set - Set or unset values of shell options and positional parameters.
57. shift - Shift positional parameters.
58. shopt - Set and unset shell options.
59. source - Execute commands from a file in the current shell.
60. suspend - Suspend shell execution.
61. test - Evaluate conditional expression.
62. time - Report time consumed by pipeline's execution.
63. times - Display process times.
64. trap - Trap signals and other events.
65. true - Return a successful result.
66. type - Display information about command type.
67. typeset - Set variable values and attributes.
68. ulimit - Modify shell resource limits.
69. umask - Display or set file mode mask.
70. unalias - Remove each NAME from the list of defined aliases.
71. unset - Unset values and attributes of shell variables and functions.
72. until - Execute commands as long as a test does not succeed.
73. variables - Common shell variable names and usage.
74. wait - Wait for job completion and return exit status.
75. while - Execute commands as long as a test succeeds.
76. { ... } - Group commands as a unit.

可以看到Bash內建的指令大概有70多個，至於Linux上全部的指令可以參考O'Reilly的Linux Command Directory。

心得感想：對於任何電腦系統，務必熟悉最重要的help指令，不知道怎麼操作就請「help」吧，但前提是你要知道有「help」啊！

相關指令：

• 確認shell的種類：echo $SHELL
• 顯示Bash的版本：echo $BASH_VERSION

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