Shell Condition Test Summary

Condition test: Recommended format 2

Format 1:test< Test expression > man test See Related Help

Format 2: [< test expression;]

Format 3: [[< test expression;]]

Description: A wildcard character can be used for pattern matching in [[]] && | | > < operators can be applied to [[]], but not in []

[[email protected] ~]# test-f file && echo 1 | | Echo 0

0

[[email protected] ~]# Touch file

[[email protected] ~]# test-f file && echo 1 | | Echo 0

1

[Email protected] ~]# test! -F file && echo 1 | | Echo 0

0

[Email protected] ~]# arg= "Martin"

[Email protected] ~]# test-z "$arg" && echo 1 | | Echo 0

0

[[Email protected] tools]# [-F file]&& echo 1 | | Echo 0

0

[[Email protected] tools]# [[-F File &&-D dir]]&& echo 1 | | Echo 0

0

File Test Operators

-F File

-D Dirrctory

-S size file exists and is not empty is true

-e exist can be a file or a directory

-R Read

-W Write

-X Excute.

-L Link

F1-nt F2 Newer than if file F1 than file F2 new is True

F1-ot F2 older than

[Email protected] tools]# mkdir Martin

[[Email protected] tools]# [-F Martin]&& echo 1 | | Echo 0

0

[[Email protected] tools]# [-D Martin]&& echo 1 | | Echo 0

1

[Email protected] tools]# [-e Martin]&& echo 1 | | Echo 0

1

Common string test operators

-Z "string" if the length is 0 is true, Z can be understood as zero

-N "string" if the length is not 0 is true, n can be understood as no zero

"String 1" = "String 2" if string 1 equals string 2 is true, you can use = = instead of =

"String 1"! = "String 2" if string 1 is not string 2 is true, but cannot use!== instead of! =

string or string variable comparisons are double-quoted and then compared

string comparison, compare symbols at both ends preferably with a space, multi-reference system script

[Email protected] tools]# sed-n ' 30,31p '/etc/init.d/network

# Check that networking are up.

["${networking}" = "no"] && Exit 6

[Email protected] tools]# martin= "Hello"

[[Email protected] tools]# ["${martin}" = "Hello"]&& echo 1 | | Echo 0

1

[[Email protected] tools]# ["${martin}" = "hello123"]&& echo 1 | | Echo 0

0

[[Email protected] tools]# [-N "abc"]&& echo 1 | | Echo 0

1

[[Email protected] tools]# [-N ""]&& echo 1 | | Echo 0

0

650) this.width=650; "src=" Http://s3.51cto.com/wyfs02/M02/89/24/wKiom1gIumHgEW9nAAA_xDwA2ao164.png "title=" 1.png " alt= "Wkiom1giumhgew9naaa_xdwa2ao164.png"/>

[[Email protected] tools]# [12-eq]&&echo 1 | | Echo 0

0

[[Email protected] tools]# [12-lt]&&echo 1 | | Echo 0

1

[[Email protected] tools]# [12-gt]&&echo 1 | | Echo 0

0

[[Email protected] tools]# [[>]]&&echo 1 | | Echo 0

0

[[Email protected] tools]# [[<]]&&echo 1 | | Echo 0

1

logical operators

The logical operator used in [] in [] is explained

-A && and

- O | | or

!                          ! Not take counter

[[Email protected] tools]# [-F "$f 1"-a-f "$f 2"]&& echo 1 | | Echo 0

1

Observing System Script NFS

# Source Networking configuration.

[-f/etc/sysconfig/network] &&. /etc/sysconfig/network

[Email protected] scripts]# sed-n ' 87,90p '/etc/init.d/nfs

["$NFSD _module"! = "Noload"-a-x/sbin/modprobe] && {

/sbin/modprobe NFSD

[-N "$RDMA _port"] &&/sbin/modprobe SVCRDMA

}

This article from "Thick tak" blog, declined reprint!

Shell Condition Test Summary