Comparison in bash shell

1. Arithmetic comparison

Operator	Describe
-eq	Equals
-ne	Not equal to
-gt	Greater than
-lt	Less than
-ge	Greater than or equal
-le	Less than or equal

Example:

[$var-eq 1] #变量等于1 return True

[$var-ne 1] #变量不等于1 return True

[$var-GT 1] #变量大于1 return True

[$var-lt 1] #变量小于1 return True

[$var-ge 1] #变量大于等于1 return True

[$var-le 1] #变量小于等于1 return True

2. String comparison

string comparison time using [[]] double brackets

The direct example illustrates:

[[$str 1 = = $str 2]] #字符串相同, return True

[[$str 1! = $str 2]] #字符串不相同, return True

[[$str 1 > $str 2]] #字符串str1的ascii码表序比str2大, return True

[[$str 2 < $STR 2]] #字符串str1的ascii码表序比str2小, return True

[-Z $str]] #字符串是空字符串, return True

[[Email protected] test]# [[-Z] "]];echo $? 0

[-N $str]] #字符串是非空字符串, return True

[[Email protected] test]# [[-N ' Sdfas ']];echo $?] 0

3. File System attribute Comparison

Direct illustrative examples

[-F $var] #变量为文件, return True

[-D $var] #变量为目录, return True

[-e $var] #变量所示的文件存在, return True

[-X $var] #变量所示的文件可以执行, return True

[-W $var] #变量所示文件可写, returns True

[-R $var] #变量所示文件可读, returns True

[Email protected] test]# ls-ltotal 4-rw-r--r--. 1 root root 1 23:47 test.sh[[email protected] test]# [[-X test.sh]];echo $? #因为test. SH does not have execute permissions, so $?   Not equal to 01[[email protected] test]# [[-W test.sh]];echo $?] 0[[email protected] test]# [[-R test.sh]];echo $?0

[-L $var] #变量所示是符号链接, return True

[-B $var] #变量为块设备文件, returns True

[-C $var] #变量为字符设备文件, returns True

[[Email protected] dev]# ls -l |grep cdrlrwxrwxrwx. 1 root root            3 Jan  1 21:34  cdrom1 -> sr0lrwxrwxrwx. 1 root root            3 JAN  1 21:34 CDRW1 -> SR0CRW-RW----.  1  root cdrom    21,   1 Jan  1 21:34  SG1BRW-RW----+ 1 root cdrom    11,   0 jan  1  21:34 sr0[[email protected] dev]# [[ -l cdrom1 ]];echo $?0[[ email protected] dev]# [[ -b cdrom1 ]];echo $?  #cdrom1是符号链接指向块设备, So it's true 0[[email protected] dev]# [[ -b sr0 ]];echo $?    .   0[[email protected] dev]# [[ -c sg1 ]];echo $? 0 

The above is the comparison of common operations in bash shell. Can be easily used in scripts.

This article from the "Ha-ha" blog, please be sure to keep this source http://10452483.blog.51cto.com/10442483/1730877

Comparison in bash shell