set (Bourne shell（sh），C shell（csh）和Korn shell（ksh）的內置函數，用于定義和確定系統環境的值)

瑞茲發表于 2020-11-28 00:56

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命令行 Unix&Linux命令 set

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在類似Unix的操作系統上，set命令是Bourne shell（sh），C shell（csh）和Korn shell（ksh）的內置函數，用于定義和確定系統環境的值。

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1 set 運行系統環境

2 set 語法

3 set 例子

set 運行系統環境

Unix&Linux

set 語法

Bourne shell (sh):

set [--aefhkntuvx[argument]]...

C shell (csh):

set [var[=value]]

set var [n] = word

Korn shell (ksh):

set [+-aefhkmnopstuvx] [+-o option]... [+-A name] [arg...]

選項：Bourne Shell（sh）

在sh中，set內置命令具有以下選項：

-	雙破折號（“ - ”）的選項表示選項列表的末尾。這個選項主要是有用的，當選項后列出的值將與破折號自己開始。
-a	標記為“導出”修改或創建的變量；以這種方式設置的環境變量將被傳遞到任何后續命令的環境中。
-e	如果命令以非零退出狀態退出，則立即退出。
-f	禁用文件名生成（globlob）。
-h	在定義功能時定位并記住功能命令（執行功能時通常會找到功能命令）。
-k	所有關鍵字參數都放置在命令環境中，而不僅僅是命令名稱前面的參數。
-n	讀取命令但不執行。
-t	讀取并執行一條命令后退出。
-u	替換時，將未設置的變量視為錯誤。
-v	讀取時打印外殼輸入行。
-x	在執行命令時打印命令及其參數。

使用+而不是-導致這些標志被關閉。這些標志也可以在調用Shell本身時使用。當前的標志集可以在變量$-中找到。其余參數是位置參數，并按順序分配給$ 1，$ 2等。如果未給出參數，則將打印所有名稱的值。

對于每個名稱，unset命令都會刪除相應的變量或函數值。不能取消設置特殊變量PATH，PS1，PS2，MAILCHECK和IF。

使用內置導出命令，將給定名稱標記為自動導出到隨后執行的命令環境。如果未提供任何參數，則會列出在當前Shell執行期間已標記為導出的變量名稱。函數名稱不會導出。

選項：C Shell（csh）

在csh中，如果未指定任何參數，則set顯示所有shell變量的值。多字值顯示為帶括號的列表。僅使用var參數，set會將一個空（null）值分配給變量var。使用var = value形式的參數時，set將value分配給var，其中value是以下之一：

word	一個單詞（或帶引號的字符串）。
（wordlist）	括號中用空格分隔的單詞列表。

值是在分配之前擴展的命令和文件名。形式set var[ n ] =word替換n'th在一個多字個字值與字。

unset刪除名稱匹配（使用文件名替換）模式的變量。所有變量都用“ unset * ”刪除；但是，如果您不知道自己在做什么，這是一個非常糟糕的主意。

選項：K Shell（ksh）

在ksh中，set命令采用以下選項：

-A

數組分配。取消設置變量名稱，并從列表arg順序分配值。如果使用+ A，則不會先取消設置變量名。

-a

定義的所有后續變量都將自動導出。

-e

如果命令的退出狀態為非零，請執行ERR 陷阱（如果已設置），然后退出。讀取配置文件時禁用此模式。

-f

禁用文件名生成（globbing）。

-h

第一次遇到時，每個命令都會成為跟蹤的別名。

-k

所有變量分配參數都放置在命令的環境中，而不僅僅是命令名稱之前的參數。

-m

后臺作業將在單獨的進程組中運行，并在完成時打印一行。在完成消息中報告后臺作業的退出狀態。在具有作業控制的系統上，對于交互式shell，此標志會自動打開。

-n

閱讀命令并檢查它們是否存在語法錯誤，但不要執行它們。忽略交互式外殼。

-o potion

該選項參數可以是下列情況之一：

allexport	與-a相同。
errexit	與-e相同。
Bgnice	所有后臺作業均以較低的優先級運行，這是默認模式。
emacs	使您進入emacs風格的嵌入式編輯器以輸入命令。
emacs	使您進入gmacs風格的嵌入式編輯器以輸入命令。
ignoreeof	Shell不會在文件末尾退出。必須使用命令出口。
keyword	與-k相同。
Markdirs	由文件名生成產生的所有目錄名稱都附加了結尾的“ / ”。
moniror	與-m相同。
noclobber	防止重定向“ > ”截斷現有文件。要求“ > \| ”以在打開文件時截斷文件。
Noexec	與-n相同。
noglob	與-f相同。
nolog	不要將功能定義保存在歷史文件中。
nounset	與-u相同。
privileged	與-p相同。
verbose	與-v相同。
Trackall	與-h相同。
vi	使您進入vi樣式內聯編輯器的插入模式，直到您單擊escape為止。此選項參數使您進入控制模式。一回發線。
viraw	在vi模式下鍵入時將處理每個字符。
xtrace	與-x相同。

如果未提供選項名稱，則將打印當前選項設置。

-p

禁用$ HOME / .profile文件的處理，并使用文件/ etc / suid_profile而不是ENV文件。只要有效uid（用戶ID）不等于真實uid，或者有效gid（組ID）不等于真實gid，就會啟用此模式。禁用此選項會使有效uid和gid設置為實際uid和gid。

-s

按字典順序對位置參數進行排序。

-t

讀取并執行一條命令后退出。

-u

替換時，將未設置的參數視為錯誤。

-v

讀取時打印外殼輸入行。

-X

在執行命令時打印命令及其參數。

關閉-x和-v標志，并停止檢查標志的參數。

請勿更改任何標志。在將$ 1設置為以-開頭的值時很有用。如果沒有參數跟隨此標志，則未設置位置參數。

使用+而不是-導致這些標志被關閉。這些標志也可以在調用Shell時使用。當前標志集可以在$-中找到。除非指定-A，否則其余參數為位置參數，并按順序分配給“ $ 1 $ 2 ...”。如果未提供任何參數，則所有變量的名稱和值都將顯示在標準輸出上。

名稱列表給定的變量將自動取消分配：它們的值和屬性將被刪除。只讀變量不能被設置。如果設置了-f標志，則名稱指的是函數名稱。解封ERRNO，LINENO，MAILCHECK，OPTARG，OPTIND，RANDOM，SECONDS，TMOUT和_刪除，即使他們隨后被分配其特殊的意義。

當使用unset時，名稱列表中給定的變量同樣未被分配：它們的值和屬性被刪除。只讀變量不能被設置。如果設置了-f標志，則名稱指的是函數名稱。解封ERRNO，LINENO，MAILCHECK，OPTARG，OPTIND，RANDOM，SECONDS，TMOUT和_刪除，即使他們隨后被分配其特殊的意義。

使用內置導出命令，將給定名稱標記為自動導出到后續執行的命令環境。前面帶有一或兩個“ * ”字符（星號）的ksh命令將按以下方式進行特殊處理：

命令之前的變量分配列表在命令完成時仍然有效。
I / O 重定向在變量分配后進行處理。
錯誤會導致包含它們的腳本中止。
在以**開頭的命令之后，以變量賦值格式的單詞將以與變量賦值相同的規則擴展。此分配意味著在=號之后執行代字號替換，并且不執行單詞拆分和文件名生成。

Bourne shell (sh):

set [--aefhkntuvx[argument]]...

C shell (csh):

set [var[=value]]

set var [n] = word

Korn shell (ksh):

set [+-aefhkmnopstuvx] [+-o option]... [+-A name] [arg...]

Options: Bourne Shell (sh)

In sh, the set built-in command has the following options:

--	An option of a double-dash ("--") signifies the end of an option list. This option is primarily useful when values listed after the options will start with a dash themselves.
-a	Mark variables that are modified or created for "export"; environment variables set in this way will be passed on to the environments of any subsequent commands.
-e	Exit immediately if a command exits with a non-zero exit status.
-f	Disable file name generation (globbing).
-h	Locate and remember function commands as functions are defined (function commands are normally located when the function is executed).
-k	All keyword arguments are placed in the environment for a command, not just those that precede the command name.
-n	Read commands but do not execute them.
-t	Exit after reading and executing one command.
-u	Treat unset variables as an error when substituting.
-v	Print shell input lines as they are read.
-x	Print commands and their arguments as they are executed.

Using + rather than - causes these flags to be turned off. These flags can also be used upon invocation of the shell itself. The current set of flags may be found in the variable $-. The remaining arguments are positional parameters and are assigned, in order, to $1, $2, etc. If no arguments are given the values of all names are printed.

For each name, the unset command removes the corresponding variable or function value. The special variables PATH, PS1, PS2, MAILCHECK, and IF cannot be unset.

With the export built-in command, the given names are marked for automatic export to the environment of subsequently executed commands. If no arguments are given, variable names that have been marked for export during the current shell's execution are listed. Function names are not exported.

Options: C Shell (csh)

In csh, If no arguments are specified, set displays the values of all shell variables. Multiword values are displayed as a parenthesized list. With the var argument alone, set assigns an empty (null) value to the variable var. With arguments of the form var = value, set assigns value to var, where value is one of:

word	A single word (or quoted string).
(wordlist)	A space-separated list of words enclosed in parentheses.

Values are command and file name expanded before being assigned. The form set var[n]=word replaces the n'th word in a multiword value with word.

unset removes variables whose names match (using file name substitution) pattern. All variables are removed by "unset *"; this is a very bad idea if you don't know what you're doing, though.

Options: K Shell (ksh)

In ksh, the set command takes the following options:

-A

Array assignment. Unset the variable name and assign values sequentially from the list arg. If +A is used, the variable name is not unset first.

-a

All subsequent variables that are defined are automatically exported.

-e

If a command has a non-zero exit status, execute the ERR trap (if set), and exit. This mode is disabled while reading profiles.

-f

Disables file name generation (globbing).

-h

Each command becomes a tracked alias when first encountered.

-k

All variable assignment arguments are placed in the environment for a command, not just those that precede the command name.

-m

Background jobs will run in a separate process group and a line will print upon completion. The exit status of background jobs is reported in a completion message. On systems with job control, this flag is turned on automatically for interactive shells.

-n

Read commands and check them for syntax errors, but do not execute them. Ignored for interactive shells.

-o option

The option argument can be one of the following:

allexport	Same as -a.
errexit	Same as -e.
bgnice	All background jobs are run at a lower priority, which is the default mode.
emacs	Puts you in an emacs-style in-line editor for command entry.
emacs	Puts you in a gmacs-style in-line editor for command entry.
ignoreeof	The shell will not exit on end-of-file. The command exit must be used.
keyword	Same as -k.
markdirs	All directory names resulting from file name generation have a trailing "/" appended.
monitor	Same as -m.
noclobber	Prevents redirection ">" from truncating existing files. Require ">\|" to truncate a file when turned on.
noexec	Same as -n.
noglob	Same as -f.
nolog	Do not save function definitions in history file.
nounset	Same as -u.
privileged	Same as -p.
verbose	Same as -v.
trackall	Same as -h.
vi	Puts you in insert mode of a vi-style in-line editor until you hit escape. This option argument puts you in control mode. A return sends the line.
viraw	Each character is processed as it is typed in vi mode.
xtrace	Same as -x.

If no option name is supplied then the current option settings are printed.

-p

Disables processing of the $HOME/.profile file and uses the file /etc/suid_profile instead of the ENV file. This mode is on whenever the effective uid (user ID) is not equal to the real uid, or when the effective gid (group ID) is not equal to the real gid. Turning this off causes the effective uid and gid to be set to the real uid and gid.

-s

Sort the positional parameters lexicographically.

-t

Exit after reading and executing one command.

-u

Treat unset parameters as an error when substituting.

-v

Print shell input lines as they are read.

-x

Print commands and their arguments as they are executed.

Turns off -x and -v flags and stops examining arguments for flags.

Do not change any of the flags; useful in setting $1 to a value beginning with -. If no arguments follow this flag then the positional parameters are unset.

Using + rather than - causes these flags to be turned off. These flags can also be used upon invocation of the shell. The current set of flags may be found in $-. Unless -A is specified, the remaining arguments are positional parameters and are assigned, in order, to "$1 $2 ...". If no arguments are given, then the names and values of all variables are printed on the standard output.

The variables given by the list of names are automatically unassigned: their values and attributes are erased. Readonly variables cannot be unset. If the -f flag is set, then the names refer to function names. Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their special meaning even if they are subsequently assigned.

When using unset, the variables given by the list of names are similarly unassigned: their values and attributes are erased. Readonly variables cannot be unset. If the -f, flag is set, then the names refer to function names. Unsetting ERRNO, LINENO, MAILCHECK, OPTARG, OPTIND, RANDOM, SECONDS, TMOUT, and _ removes their special meaning even if they are subsequently assigned.

With the export built-in command, the given names are marked for automatic export to the environment of subsequently-executed commands. ksh commands that are preceded by one or two "*" characters (asterisks) are treated specially in the following ways:

Variable assignment lists preceding the command remain in effect when the command completes.
I/O redirections are processed after variable assignments.
Errors cause a script that contains them to abort.
Words, following a command preceded by ** that are in the format of a variable assignment, are expanded with the same rules as a variable assignment. This assignment means that tilde substitution is performed after the = sign and word splitting and file name generation are not performed.

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set 例子

set PATH="/bin:/usr/bin:/usr/sbin:usr/local/bin"

在csh中，此命令設置環境變量PATH，以便外殼程序將按該順序在/ bin，/ usr / bin，/ usr / sbin和/ usr / local / bin目錄中搜索文件。

set PATH="/bin:/usr/bin:/usr/sbin:usr/local/bin"

In csh, this command sets the environment variable PATH, such that the shell will search for files in the /bin, /usr/bin, /usr/sbin and /usr/local/bin directories, in that order.

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其他命令行

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set (Bourne shell（sh），C shell（csh）和Korn shell（ksh）的內置函數，用于定義和確定系統環境的值)

set 運行系統環境

set 語法

set 例子

其他命令行

set (Bourne shell（sh），C shell（csh）和Korn shell（ksh）的內置函數，用于定義和確定系統環境的值)