如何使用 Bash 检查文件是否包含特定字符串
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How to check if a file contains a specific string using Bash
提问by Hakim
I want to check if a file contains a specific string or not in bash. I used this script, but it doesn't work:
我想在 bash 中检查文件是否包含特定字符串。我使用了这个脚本，但它不起作用：
if [[ 'grep 'SomeString' $File' ]];then
# Some Actions
fi
What's wrong in my code?
我的代码有什么问题？
回答by Igor Chubin
if grep -q SomeString "$File"; then
Some Actions # SomeString was found
fi
You don't need [[ ]]here. Just run the command directly. Add -qoption when you don't need the string displayed when it was found.
你不需要[[ ]]这里。直接运行命令即可。-q当您不需要在找到时显示的字符串时添加选项。
The grepcommand returns 0 or 1 in the exit code depending on
the result of search. 0 if something was found; 1 otherwise.
该grep命令根据搜索结果在退出代码中返回 0 或 1。0 如果找到了东西；1 否则。
$ echo hello | grep hi ; echo $?
1
$ echo hello | grep he ; echo $?
hello
0
$ echo hello | grep -q he ; echo $?
0
You can specify commands as an condition of if. If the command returns 0 in its exitcode that means that the condition is true; otherwise false.
您可以将命令指定为 的条件if。如果该命令在其退出代码中返回 0，则表示条件为真；否则为假。
$ if /bin/true; then echo that is true; fi
that is true
$ if /bin/false; then echo that is true; fi
$
As you can see you run here the programs directly. No additional []or [[]].
如您所见，您可以直接在此处运行程序。没有额外的[]或[[]]。
回答by Benoit
In addition to other answers, which told you how to do what you wanted, I try to explain what was wrong (which is what you wanted.
除了告诉您如何做您想做的其他答案之外，我还尝试解释出了什么问题（这就是您想要的。
In Bash, ifis to be followed with a command. If the exit code of this command is equal to 0, then the thenpart is executed, else the elsepart if any is executed.
在 Bash 中，if后面是一个命令。如果此命令的退出代码等于 0，则then执行该else部分，否则执行该部分（如果有）。
You can do that with any command as explained in other answers: if /bin/true; then ...; fi
您可以使用其他答案中所述的任何命令执行此操作： if /bin/true; then ...; fi
[[is an internal bash command dedicated to some tests, like file existence, variable comparisons. Similarly [is an external command (it is located typically in /usr/bin/[) that performs roughly the same tests but needs ]as a final argument, which is why ]must be padded with a space on the left, which is not the case with ]].
[[是专用于某些测试的内部 bash 命令，例如文件存在、变量比较。类似的[还有一个外部命令（它通常位于/usr/bin/[），它执行大致相同的测试，但需要]作为最后一个参数，这就是为什么]必须在左侧填充一个空格，而]].
Here you needn't [[nor [.
在这里你不需要[[也不需要[。
Another thing is the way you quote things. In bash, there is only one case where pairs of quotes do nest, it is "$(command "argument")". But in 'grep 'SomeString' $File'you have only one word, because 'grep 'is a quoted unit, which is concatenated with SomeStringand then again concatenated with ' $File'. The variable $Fileis not even replaced with its value because of the use of single quotes. The proper way to do that is grep 'SomeString' "$File".
另一件事是你引用事物的方式。在 bash 中，只有一种情况会嵌套引号对，它是"$(command "argument")". 但是 in'grep 'SomeString' $File'你只有一个词，因为'grep '是一个带引号的单元，它与 连接，SomeString然后再与 连接' $File'。$File由于使用了单引号，该变量甚至不会被其值替换。这样做的正确方法是grep 'SomeString' "$File"。
回答by Lahiru Chandima
In case if you want to check whether file does notcontain a specific string, you can do it as follows.
如果要检查文件是否不包含特定字符串，可以按如下方式进行。
if ! grep -q SomeString "$File"; then
Some Actions # SomeString was not found
fi
回答by Nevin Raj Victor
##To check for a particular string in a file
cd PATH_TO_YOUR_DIRECTORY #Changing directory to your working directory
File=YOUR_FILENAME
if grep -q STRING_YOU_ARE_CHECKING_FOR "$File"; ##note the space after the string you are searching for
then
echo "Hooray!!It's available"
else
echo "Oops!!Not available"
fi
回答by lzap
Shortest (correct) version:
最短（正确）版本：
grep -q "something" file; [ $? -eq 0 ] && echo "yes" || echo "no"
can be also written as
也可以写成
grep -q "something" file; test $? -eq 0 && echo "yes" || echo "no"
but you dont need to explicitly test it in this case, so the same with:
但是在这种情况下您不需要显式测试它，因此与以下内容相同：
grep -q "something" file && echo "yes" || echo "no"
回答by SupermanKelly
grep -q [PATTERN] [FILE] && echo $?
The exit status is 0(true) if the pattern was found; otherwise blankstring.
0如果找到模式，则退出状态为(true)；否则为空字符串。
回答by Shubham Khatri
In case you want to checkif the string matches the whole line and if it is a fixed string, You can do it this way
如果您想检查字符串是否与整行匹配并且它是固定字符串，您可以这样做
grep -Fxq [String] [filePath]
example
例子
searchString="Hello World"
file="./test.log"
if grep -Fxq "$searchString" $file
then
echo "String found in $file"
else
echo "String not found in $file"
fi
From the man file:
从人文件：
-F, --fixed-strings
Interpret PATTERN as a list of fixed strings, separated by newlines, any of
which is to be matched.
(-F is specified by POSIX.)
-x, --line-regexp
Select only those matches that exactly match the whole line. (-x is specified by
POSIX.)
-q, --quiet, --silent
Quiet; do not write anything to standard output. Exit immediately with zero
status if any match is
found, even if an error was detected. Also see the -s or --no-messages
option. (-q is specified by
POSIX.)
回答by user5854766
if grep -q [string] [filename]
then
[whatever action]
fi
Example
例子
if grep -q 'my cat is in a tree' /tmp/cat.txt
then
mkdir cat
fi
回答by vgokul129
Try this:
尝试这个：
if [[ $(grep "SomeString" $File) ]] ; then
echo "Found"
else
echo "Not Found"
fi
回答by madarekrap
I done this, seems to work fine
我这样做了，似乎工作正常
if grep $SearchTerm $FileToSearch; then
echo "$SearchTerm found OK"
else
echo "$SearchTerm not found"
fi
