If Judgment statement in Shell

If condition test Type: File test, digital test, string test

If statement structure:

• If ...; Then ...; Fi

• If ...; Then ...; else ...; Fi

Conditional test expression:

• [Expression]
• [[Expression]]
• Test expression

Digital test: Note

1. Only integer tests are possible
2. if test 3-eq $V 2 equivalent to If [3-eq $V 2]

"3-eq $V 2" equals

"3-ne $V 2" range

"3-lt $V 2" is less than

-le less than or equal to-gt greater than-ge greater than or equal

String test:Note

1. When you want to make a decimal comparison, you cannot use the method of the number test, use a string test
2. String comparison in Shell is only =, no = =
3. String testing is best done using "" to bring up strings

[[$V = $v]] Pattern match if the 4 starts with true

[[$V = "["]] character match if $v equals to True

[-Z "$V"]-Z means the string is empty

[-N "$V"]-n means the string is not empty

File test:

-e file Test files exist

-F file Test is a normal file

-D FILE Test Specifies whether the path is a directory

。。。

A good solution to writing a case:

• To determine the NFS version

For V in ...

Lockp=lockd

[$V = []] && LOCKP=NFSD

SSH $SERVER $lsLocks | grep $LOCKP

Done

1. Package the lock, then use SSH to execute command 2. Use simplified if judgment

• Judging kernel version

If Judgment statement in Shell