当符号链接使用sh和bash的区别 [英] difference between sh and bash when symlink is used

问题描述

我有一个使用进程替换

该脚本是：

  #!/bin/bash
  while read line
  do
    echo "$line"
  done < <( grep "^abcd$" file.txt )

当我使用运行脚本SH file.sh 我得到以下输出

When I run the script using sh file.sh I get the following output

$sh file.sh
file.sh: line 5: syntax error near unexpected token `<'
file.sh: line 5: `done < <( grep "^abcd$" file.txt )'

当我运行使用庆典file.sh 脚本，该脚本的工作原理。

When I run the script using bash file.sh, the script works.

有趣的是， SH 是软链接映射到 /斌/ bash的。

$ which bash
/bin/bash
$ which sh
/usr/bin/sh
$ ls -l /usr/bin/sh
lrwxrwxrwx 1 root root 9 Jul 23  2012 /usr/bin/sh -> /bin/bash
$ ls -l /bin/bash
-rwxr-xr-x 1 root root 648016 Jul 12  2012 /bin/bash

我测试，以确保符号链接正在使用以下遵循我的外壳：

I tested to make sure symbolic links are being followed in my shell using the following:

$ ./a.out
hello world
$ ln -s a.out a.link
$ ./a.link
hello world
$ ls -l a.out
-rwx--x--x 1 xxxx xxxx 16614 Dec 27 19:53 a.out
$ ls -l a.link
lrwxrwxrwx 1 xxxx xxxx 5 May 14 14:12 a.link -> a.out

我无法理解为什么 SH file.sh 不执行为 /斌/ bash的file.sh 因为 SH 是一个符号链接 /斌/庆典。

I am unable to understand why sh file.sh does not execute as /bin/bash file.sh since sh is a symbolic link to /bin/bash.

任何见解将大大AP preciated。谢谢你。

Any insights will be much appreciated. Thanks.

推荐答案

在sh的时候，bash的进入POSIX
       启动文件后模式下读取。替代的过程中没有POSIX模式的认可。据POSIX，≤（富）应当从命名的文件直接输入（富）。 （嗯，这是，根据我的标准读数。语法是模糊的，在许多地方。）

When invoked as sh, bash enters posix mode after the startup files are read. Process substitution is not recognized in posix mode. According to posix, <(foo) should direct input from the file named (foo). (Well, that is, according to my reading of the standard. The grammar is ambiguous in many places.)

Edit：从 bash的手动

The following list is what’s changed when ‘POSIX mode’ is in effect:
...
Process substitution is not available.

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