21. Self-Learning Linux road: File test, parameter rotation

Bash knowledge points for file testing:

Knowledge Review:

Character test:

Format: Test expression

: [Expression]

: [[Expression]]

Integer test:

Format: Test expression

: [Expression]

: [[Expression]]

File test:

Monocular test:

-e/path/to/file: Test file exists

-a/path/to/file: Test file exists

-f/path/to/file: Determine if the file is a normal file

-d/path/to/file: Determine if the file is a directory file

-b/path/to/file: Determine if the file is a block device file

-c/path/to/file: Determine if the file is a character device file

-H or-l/path/to/file: Determine if the file is a symbolic link file

-p/path/to/file: Determine if the file is a pipe file

-s/path/to/file: Determine if a file exists and is a socket file

-r/path/to/file: Determines whether the current file exists and whether the current user has readable permissions on the file

-w/path/to/file: Determines whether the current file exists and whether the current user has write access to the file

-x/path/to/file: Determines whether the current file exists and whether the current user has execute permissions on the file

-s/path/to/file: Determine if the current file exists and its contents are empty

Binocular test:

File1-nt file2: File 1 is newer than file 2 (modification time), if file 1 exists, file 2 does not exist, also think File1 update

File1-ot file2: File 1 is older than file 2

File1-ef file2: Does file 1 and file 2 refer to the same device file

Example 1: Create the file if/TMP/HELLO.R does not exist

#!/bin/bash

Filename=/tmp/hello.r

[-E $fileName]| | mkdir $fileName

Example 2: If the current file has read access to the profile, we will load it into

In the script, the method of loading the configuration in another file

Method 1:source/path/to/somefile or. /path/to/somefile

The contents of the configuration file are as follows:/tmp/script/myscript.conf

Username=tom

filename=/etc/passwd

#!/bin/bash

#configFile =/tmp/script/myscript.conf

[-r/tmp/script/myscript.conf] &&/tmp/script/myscript.conf

Username=$[username:-testuser]

Echo $userName

Example 3: Download a file in a script using the local file download tool wget

#!/bin/bash

Url= ' Http://172.16.0.1/centos6.5repo '

which wget &>/dev/null | | Exit 5

Downloader= ' which wget '

[-X $downloader] | | Exit 6

$downloader $url

Example 4: Write a script to complete the following tasks

1. Assist/var/logs files to the/tmp/logs directory, respectively.

2. Use cp-r when copying a directory

3. When copying files, use CP

4. Copy the linked file cp-d

5. The remaining use of cp-a

#!/bin/bash

#

Targetdir= '/tmp/logs '

[-e $targetDir] | | mkdir $targetDir

For FileName in/var/log/*; Do

If [-D $fileName]; Then

Copycommand= ' Cp-r '

Elif [-F $flieName]; Then

Copycommand= ' CP '

elif [-H $fileName];then

Copycommand= ' cp-d '

Else

Copycommand= ' Cp-a '

Fi

$copyCommand $fileName $targetDir

Done

Bash point of Knowledge: Position parameter rotation (SHIFT)

Write a script that requires the script to be accompanied by parameters, the script function for the parameters and.

#!/bin/bash

#

Declare-i sum=0

For i in ' seq 1 $# '; Do

Let sum+= $i

Shift

Done

Echo $sum

Write a script that uses the following form

Userinfo.sh-u Username [-v {1|2}]

The-u option is used to specify the user, and the script displays the user's UID and GID

If you use the-V option at the same time

The value after-V is 1, and the user's home directory path is displayed extra

The value after-V is 2, and the user's home directory path and Shell are displayed extra

#!/bin/bash

#

[$#-lt 2] && echo "Too less argements, quit" && exit 3

if [["$" = = "-U"]];then

Username= "$"

Shift 2

Fi

If [$#-ge 2] && ["$" = = "-V"];then

Verflag=$2

Fi

If [-N $verFlag];then

if! [[$verFlag =~ [012]]];then

echo "Wrong parameter"

echo "Usage: ' basename '-u username-v {1|2}"

Exit 4

Fi

Fi

#echo $userName $verFlag

If [$verFlag-eq 1];then

grep "^ $userName"/etc/passwd | Cut-d:-f1,3,4,6

elif [$verFlag-eq 2];then

grep "^ $userName"/etc/passwd | Cut-d:-f1,3,4,6,7

Else

grep "^ $userName"/etc/passwd | Cut-d:-f1,3,4

Fi

　　　　　

　　　　　　

　　　　　　　　　　　　

21. Self-Learning Linux path: File test, parameter rotation