bash：检查字符串是否以“/*”开头
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bash: check if string starts with "/*"
提问by much
In a bash-script I need to check if the string $HEADERstarts with the character sequence "/*". I was trying:
在 bash 脚本中，我需要检查字符串是否$HEADER以字符序列“/*”开头。我在尝试：
if [ $(echo $HEADER | cut -c 1-2) = '/*' ]
It's not working as expected. It seems that the string is compared to the file list of the root directory.
它没有按预期工作。似乎将字符串与根目录的文件列表进行了比较。
How can I protect the characters / and * to be interpreted from the shell?
如何保护字符 / 和 * 以从 shell 解释？
To protect the characters with a backslash isn't working either.
用反斜杠保护字符也不起作用。
回答by Jahid
This should work:
这应该有效：
if [[ $HEADER = '/*'* ]]
Another solution would be:
另一种解决方案是：
if [ "${HEADER:0:2}" = '/*' ]
Or
或者
if [[ "${HEADER:0:2}" = '/*' ]]
回答by chepner
The problem is that the result of the command substitution is subject to file name generation. You need to quote that, as well as the expansion of $HEADERin the command substitution.
问题是命令替换的结果受文件名生成的影响。您需要引用that以及$HEADER命令替换中的 扩展。
if [ "$(echo "$HEADER" | cut -c 1-2)" = '/*' ]
Since you are using bash, using the [[command (which can perform pattern matching) is a superior solution though, as Jahid has already answered.
由于您正在使用bash，因此使用该[[命令（可以执行模式匹配）是一个很好的解决方案，因为 Jahid 已经回答了。
if [[ $HEADER = '/*'* ]]
回答by dhke
You already have a few solutions, but
您已经有一些解决方案，但是
[ "${HEADER#/\*}" != "${HEADER}" ]
works with POSIX shellswithout using external tools (not counting [) or bashisms.
作品有POSIX壳，而无需使用外部工具（不包括[）或bash化。
Interestingly enough, this approach was missing from the marked duplicate.
有趣的是，标记的重复项中缺少这种方法。
回答by GMichael
This should help
这应该有帮助
if [[ $(echo $HEADER | grep -E '^\/\*' | wc -l) -gt 0 ]]
