Shell script: test command if-then for while learning notes

Test File OPERATOR:

-B file: if the file is a special file, it is true.

-C file: if the file is a special character file, it is true.

-D file: if the file is a directory, it is true.

-E file: true if the file exists

-F file: if the file is a normal file, it is true.

-G file: If the SGID bit of the file is set, it is true.

-G file: true if the file exists and belongs to the group

-K file: true if the adhesion bit of the file is set

-O file: true if the file exists and belongs to the user

-P file: if the file is a named pipe, it is true.

-R file: true if the file is readable

-S file: true if the file length is not zero

-S file: if the file is a special socket file, it is true.

-T fd: If fd is an open file descriptor connected to a terminal (fd is 1 by default), it is true.

-U file: If the SUID bit of the file is set, it is true.

-W file: true if the file is writable

-X file: true if the file is executable

If-then structured command instance:

file=test1touch fileif [ -s file ]then        echo " The file file exits and has data in it"else        echo " The file file exits ,but  has not  data in it"fidate > fileif [ -s file ]then        echo "the file file has data in it"else        echo "the file file is also empty ,no data hummm"fiif [ 1.c -nt one2.c ]then        echo "1.c is newer than one2.c"else        echo "1.c is not newer than one2.c"fi

For command:

For var in list
Do
Commands
Done

Instance:

List = "one one2 one4 one5" list = $ list "one6" // Add new data to an existing variable for state in $ listdo echo "state is $ state" done result :. /forteststate is onestate is one2state is one4state is one5state is one6

Read the value from the command: file = "states" for state in 'cat $ file' do echo "visit word $ state" done ~

While command

Format:

While the command
Do
Other commands
Done

Instance:

Var1 = 10 # assign a value if there is no space or a space. For example,/last: 3rd rows: [:-gt: expect the echo "var1 is $ var1" while [$ var1-gt 0] do echo "the var1 is $ var1" var1 = $ [$ var1-1] done

Result:

the var1 is 10the var1 is 9the var1 is 8the var1 is 7the var1 is 6the var1 is 5the var1 is 4the var1 is 3the var1 is 2the var1 is 1