Test conditions
1, the test document
2, an integer of test
3, the logic test string
if statement:
if a single branch statement
if dual branch statement
if a multi-branch statements
nested if statements
test command:
Test-specific expression is established when the condition is met, the test statement returns 0, otherwise other values.
Format 1: test conditional expressions
Format 2: [conditional expression] // Note that there are spaces
File test
Refers to the test document is based on the given path name, it is determined that the corresponding file or directory, or determining whether the file is readable, writable, executable, etc.
Common test operators:
-d: test whether a directory (Directory)
-e: to test whether a directory or file exists (Exist)
-f: Test whether the file (File)
-r: test whether the current user has permission to read (the Read)
-w: test whether the current user has permission to write (the write)
-x: to test whether the current user has permission to perform (eXcute)
Practice:
Formats:
test -d / etc / sysconfig (Test in / etc sysconfig directory exists)
echo $? (output value is 0, then the condition is true)
Format II:
[-D / etc / sysconfig]
echo $? (Output value of 1, the conditions are not satisfied)
Integer value comparison:
Format: [integer operator integer of 2]
Common test operators:
-eq: equal (Equal)
-ne: is not equal to (Not Equal)
-gt: greater than (the Greater Than)
-LT-: less than (Lesser Than)
-le: less than or equal to (Lesser or Equal)
-ge: greater than or equal to ( Greater or Equal)
String comparison
Format 1: [String String 1 = 2]
[String String = 1 2!]
Format 2: [String the -Z]
common test operator i:
=: the same string content
=:! String content ! different, represent opposite meaning
-z: the string is empty
Logic test
Format 1: [Expression 1] operator [Expression 2] ...
Format 2: Command 1 Command 2 ... operator
Common Options
-a or &&: logical AND, "and" means
-o or | |: logical or, "or" means
! : No logic, that "no" means
if statement:
Single branch structure :
if condition test operation
then
the command sequence
fi
Two-branch structure:
if condition test operation
then
the command sequence. 1
the else
command sequence 2
Fi
Multi-branch structure:
if condition test operation
then
the command sequence. 1
elif conditional test operation 2
then
command sequence 2
the else
command sequence. 3
Fi
if nested statements:
Purpose: jogging for the game, 10 seconds into the final, after entering the sex, were prompted to enter the men's or women's, to determine the use of multiple nested if realized
