Share 9 Linux Shell Scripting Tips for Practice and Interviews

Precautions

1) Add interpreter at the beginning: #!/bin/bash

2) Use four spaces for syntax indentation and add more comments.

3) Naming suggestion rules: variable names are capitalized, local variables are lowercase, function names are lowercase, and the names should reflect their actual functions.

4) By default, variables are global. In a function, the variable local is specified as a local variable to avoid polluting other scopes.

5) There are two commands that can help me debug the script: set -e exits the script when a non-zero result is encountered, and set -x prints the execution process.

6) When writing a script, be sure to test it first before putting it into production.

1 Get a random string or number

Get a random 8-bit string:

Get a random 8-digit number:

cksum: print CRC checksum statistics bytes

2 Define a color output string function

The function keyword defines a function and can be added or not.

3. Create users in batches

4 Check if the package is installed

5 Check service status

6 Check host survival status

Method 1: Put the wrong IP into an array to determine whether the ping fails three times

Method 2: Put the number of errors into the FAIL_COUNT variable to determine whether the ping failed three times

Method 3: Use the for loop to exit the loop if the ping succeeds. If it does not exit, it will print "ping failed"

7. Monitor CPU, memory and disk utilization

1) CPU

Use the vmstat tool to analyze CPU statistics.

2) Memory

3) Hard disk

8 Batch host disk utilization monitoring

Prerequisite: SSH non-interactive login or key login is used for the monitoring and monitored ends.

Write a configuration file to save the SSH connection information of the monitored host. The file content format is: IP User Port

9. Check website availability

1) Check URL availability

2) Determine the availability of the URL three times

The idea is the same as checking the host survival status above.

Summarize

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