在 bash 脚本中使用标志
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use of flags in bash script
提问by iwekesi
Scripts in linux start with some declaration like :
linux 中的脚本以一些声明开头，例如：
#!/bin/bash
#!/bin/bash
Correct me if I am wrong : this probably says which shell to use.
如果我错了，请纠正我：这可能说明要使用哪个 shell。
I have also seen some scripts which say :
我还看到一些脚本说：
#!/bin/bash -ex
#!/bin/bash -ex
what is the use of the flags -ex
标志 -ex 的用途是什么
回答by pavnik
#!/bin/bash -ex
<=>
#!/bin/bash
set -e -x
Man Page (http://ss64.com/bash/set.html):
手册页 ( http://ss64.com/bash/set.html)：
-e Exit immediately if a simple command exits with a non-zero status, unless
the command that fails is part of an until or while loop, part of an
if statement, part of a && or || list, or if the command's return status
is being inverted using !. -o errexit
-x Print a trace of simple commands and their arguments
after they are expanded and before they are executed. -o xtrace
UPDATE:
更新：
BTW, It is possible to set switches without script modification.
顺便说一句，无需修改脚本即可设置开关。
For example we have the script t.sh:
例如，我们有脚本t.sh：
#!/bin/bash
echo "before false"
false
echo "after false"
And would like to trace this script: bash -x t.sh
并想跟踪这个脚本： bash -x t.sh
output:
output:
+ echo 'before false'
before false
+ false
+ echo 'after false'
after false
For example we would like to trace script and stop if some command fail (in our case it will be done by command false): bash -ex t.sh
例如，我们想跟踪脚本并在某些命令失败时停止（在我们的例子中它将由 command 完成false）：bash -ex t.sh
output:
output:
+ echo 'before false'
before false
+ false
回答by Matei David
These are documented under setin the SHELL BUILTIN COMMANDSsection of the man page:
这些记录在手册页set的SHELL BUILTIN COMMANDS部分中：
-ewill cause Bash to exit as soon as a pipeline (or simple line) returns an error-xwill case Bash to print the commands before executing them
-e一旦管道（或简单的行）返回错误，就会导致 Bash 退出-x将案例 Bash 在执行之前打印命令
回答by Gilles Quenot
-e
is to quit the script on any error
是在出现任何错误时退出脚本
-x
is the debug mode
是调试模式
Check bash -x commandand What does set -e mean in a bash script?
