Cron Job

Reference: https://crontab.guru/

Sample Script (sample.sh):

#!/bin/bash

name="dev"
echo "$name" >> /tmp/demo.txt

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Add Execute Permission

chmod +x sample.sh

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Schedule with Crontab

crontab -e

Add the following line with your desired cron expression:

* * * * *  /root/sample.sh

This runs sample.sh every minute. Adjust the expression as needed using crontab.guru.

Cron Expression Format

* * * * *  command
│ │ │ │ │
│ │ │ │ └── Day of week  (0–7, Sun=0 or 7)
│ │ │ └──── Month        (1–12)
│ │ └────── Day of month (1–31)
│ └──────── Hour         (0–23)
└────────── Minute       (0–59)

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Functions

#!/bin/bash

# Function with a parameter
greeting() {
    echo "Executed by user: $1"
}

greeting "devops"


# Function with local variable and return value
add() {
    local sum=$(( $1 + $2 ))
    echo "The total is: $sum"
}

add 4 6

Key Points

• Use local inside functions to avoid polluting the global scope.
• Pass arguments to functions using $1, $2, etc.
• Functions must be defined before they are called.

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wc (Word Count)

wc [options] filename

Flag	Description
-l	Count lines
-w	Count words
-c	Count bytes/characters
-m	Count characters

Examples:

wc -l /tmp/demo.txt       # Count lines in file
wc -w sample.sh           # Count words in script
wc -c sample.sh           # Count bytes in script
wc /tmp/demo.txt          # Show lines, words, and bytes together