The Linux grep command is used to find strings that meet the criteria in a file.
The grep directive is used to find files with the specified sample style. If the content of a file is found to meet the specified sample style, the preset grep directive will display the column containing the sample style. If no file name is specified, or the file name given is "-", the grep instruction will read data from the standard input device.
grep -q Introduction
For if logic judgment Quiet mode, no standard output is printed. If there is a matching content, the status value 0 will be returned immediately.
usage
grep -q parameter[Request for what to look for] file name
Example
Example 1
[root@localhost ~]# cat ## Test datad e j s q u z c b [root@localhost ~]# grep "s" ## Direct output matching resultss q u [root@localhost ~]# echo $? ## Output 0 means the match is successful0 [root@localhost ~]# grep -q "s" ## -q option means silent output [root@localhost ~]# echo $? ## Output 0 means the match is successful0
Example 2
[root@localhost ~]# cat ## Test datanihao nihaooo hello [root@localhost ~]# grep hello ## Direct output matching resultshello [root@localhost ~]# echo $? ## Output 0 means the match is successful0 [root@localhost ~]# grep -q hello ## -q option represents silent output [root@localhost ~]# echo $? ## Output 0 means the match is successful0
#Judge whether hello text is found, if there is, output yes, if there is no, output no; use silent output[root@localhost ~]# if grep -q hello ; then echo yes;else echo no; fi yes [root@localhost ~]# if grep -q word ; then echo yes; else echo no; fi no
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