使用`sh`和`source`有什么区别? [英] What is the difference between using `sh` and `source`?

问题描述

sh和source有什么区别?

source: source filename [arguments]
    Read and execute commands from FILENAME and return.  The pathnames
    in $PATH are used to find the directory containing FILENAME.  If any
    ARGUMENTS are supplied, they become the positional parameters when
    FILENAME is executed.

对于man sh:

NAME
       bash - GNU Bourne-Again SHell

SYNOPSIS
       bash [options] [file]

COPYRIGHT
       Bash is Copyright (C) 1989-2004 by the Free Software Foundation, Inc.

DESCRIPTION
       Bash  is  an sh-compatible command language interpreter that executes commands read from the standard input or from a file.  Bash also incorporates
       useful features from the Korn and C shells (ksh and csh).

       Bash is intended to be a conformant implementation of the IEEE POSIX Shell and Tools specification (IEEE Working Group 1003.2).

推荐答案

调用source(或其别名.)时，您会在 current 中加载并执行bash脚本 bash进程.因此，您可以

When you call source (or its alias .), you load and execute a bash script into the current bash process. So you can

• 读取在源脚本中设置的变量
• 使用其中定义的功能.
• 甚至在脚本执行此操作的情况下执行fork和/或子进程.

调用sh时，将启动运行新会话/bin/sh的 fork (子过程或 child )，该会话通常是象征性的链接到bash.在这种情况下，子脚本完成时，将删除由子脚本设置的环境变量.

When you call sh, you initiate a fork (sub-process or child) that runs a new session of /bin/sh, which is usually a symbolic link to bash. In this case, environment variables set by the sub-script would be dropped when the sub-script finishes.

警告:sh可能是到另一个外壳的符号链接.

Caution: sh could be a symlink to another shell.

例如，如果您想以特定方式更改当前工作目录，则无法执行

For example, if you want to change current working directory by a specific manner, you could not do

$ cat <<eof >myCd2Doc.sh
#!/bin/sh
cd /usr/share/doc
eof

$ chmod +x myCd2Doc.sh

这不会达到您的期望:

$ cd /tmp
$ pwd
/tmp
$ ~/myCd2Doc.sh
$ pwd
/tmp

因为当前工作目录是环境的一部分，并且myCd2Doc.sh将在 subshel​​l 中运行.

because current working dir is part of environment and myCd2Doc.sh would run in a subshell.

但是:

$ cat >myCd2Doc.source <<eof
# Shell source file
myCd2Doc() {
    cd /usr/share/doc
}
eof

$ . myCd2Doc.source
$ cd /tmp
$ pwd
/tmp
$ myCd2Doc
$ pwd
/usr/share/doc

我写了一个 mycd 函数的小样本(使用

I wrote a little sample of mycd function (with bash completion based on bash Associative Array).

$ cd /tmp
printf %b '\43\41/bin/bash\necho This is level \44SHLVL.\n' >qlvl.sh

$ bash qlvl.sh 
This is level 2.

$ source qlvl.sh 
This is level 1.

小递归

$ cat <<eoqlvl2 >qlvl2.sh 
#!/bin/bash

export startLevel
echo This is level $SHLVL started:${startLevel:=$SHLVL}.
((SHLVL<5)) && ./qlvl2.sh
eoqlvl2
$ chmod +x qlvl2.sh

$ ./qlvl2.sh 
This is level 2 started:2.
This is level 3 started:2.
This is level 4 started:2.
This is level 5 started:2.

$ source qlv2.sh 
This is level 1 started:1.
This is level 2 started:1.
This is level 3 started:1.
This is level 4 started:1.
This is level 5 started:1.

一点点

$ sed '$a ps --sid $SID fw' qlvl.sh >qlvl3.sh
$ chmod +x qlvl3.sh 
$ export SID
$ read SID < <(ps ho sid $$)
$ echo $SID $$
8983 8983

(当前 PID ($$ == 进程ID )是与 SID (会话ID ).并非总是如此.)

( Current PID ($$ == process Id) are same identifier than SID (session ID). It's not alway true.)

$ ./qlvl3.sh 
This is level 2.
  PID TTY      STAT   TIME COMMAND
 8983 pts/10   Ss     0:00 /bin/bash
10266 pts/10   S+     0:00  \_ /bin/bash ./qlvl3.sh
10267 pts/10   R+     0:00      \_ ps --sid 8983 fw

$ . qlvl3.sh 
This is level 1.
  PID TTY      STAT   TIME COMMAND
 8983 pts/10   Ss     0:00 /bin/bash
10428 pts/10   R+     0:00  \_ ps --sid 8983 fw

点.是source的别名.因此，两个命令之间的唯一区别是将 slash 替换为 space .

Dot . is an alias of source. So the only difference between two command are slash replaced by space.

$ printf %b '\43\41/bin/bash\necho Ending this.\nsleep 1;exit 0\n' >finalTest.sh

$ bash finalTest.sh 
Ending this.

$ source finalTest.sh
Ending this.

...您可能会注意到两种语法之间的不同行为. ;-)

... You may notice a different behaviour between the two syntaxes. ;-)

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