不匹配时 sed 的返回值 [英] Return value of sed for no match

问题描述

我正在使用 sed 在运行时更新我的​​ JSON 配置文件.有时，当 JSON 文件中的模式不匹配时，sed 仍然以返回码 0 退出.

I'm using sed for updating my JSON configuration file in the runtime. Sometimes, when the pattern doesn't match in the JSON file, sed still exits with return code 0.

返回 0 表示成功完成，但是如果 sed 没有找到正确的模式并更新文件，为什么它返回 0?有解决方法吗?

Returning 0 means successful completion, but why does sed return 0 if it doesn't find the proper pattern and update the file? Is there a workaround for that?

推荐答案

正如@cnicutar 所评论的，命令的返回码表示命令是否成功执行.与您在代码/脚本中实现的逻辑无关.

as @cnicutar commented, the return code of a command means if the command was executed successfully. has nothing to do with the logic you implemented in the codes/scripts.

所以如果你有:

echo "foo"|sed '/bar/ s/a/b/'

sed 将返回 0 但如果你写了一些语法/表达式错误，或者输入/文件不存在，sed 无法执行你的请求，sed 将返回 1.

sed will return 0 but if you write some syntax/expression errors, or the input/file doesn't exist, sed cannot execute your request, sed will return 1.

解决方法

这实际上不是解决方法.sed 有 q 命令:(来自手册页):

this is actually not workaround. sed has q command: (from man page):

 q [exit-code]

在这里您可以根据需要定义退出代码.例如 '/foo/!{q100};如果 foo 不存在，{s/f/b/}' 将以代码 100 退出，否则执行替换 f->b 并以代码 0 退出.

here you can define exit-code as you want. For example '/foo/!{q100}; {s/f/b/}' will exit with code 100 if foo isn't present, and otherwise perform the substitution f->b and exit with code 0.

匹配案例:

kent$  echo "foo" | sed  '/foo/!{q100}; {s/f/b/}'
boo
kent$  echo $?
0

不匹配的情况:

kent$ echo "trash" | sed  '/foo/!{q100}; {s/f/b/}'
trash
kent$ echo $?
100

我希望这能回答您的问题.

I hope this answers your question.

编辑

我必须补充一点，上面的例子仅用于单行处理.我不知道你的确切要求.当您想获得 exit 1 时.单行不匹配或整个文件.如果整个文件不匹配，你可以考虑 awk，甚至在你的文本处理之前做一个 grep...

I must add that, the above example is just for one-line processing. I don't know your exact requirement. when you want to get exit 1. one-line unmatched or the whole file. If whole file unmatching case, you may consider awk, or even do a grep before your text processing...

这篇关于不匹配时 sed 的返回值的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！