Wednesday, 28 October 2020

Bash Scripting Get Arguments from Command Line

Bash Scripting Get Arguments from Command Line

Bash Scripting

In Linux, all tasks from execution of services to loading and unloading of modules are carried out by programs and all programs need to be executed. You use the commands to access all the basic features of kernel. Shell scripting is a way to automate such tasks, and bash is one of the language, that has capabilities enough to be called as scripting as well as a language that can be used for programming on the POSIX platform, for small tasks.  Bash Scripting else if statement


Get Arguments from Command Line

Bash script can read input from command line argument like other programming language. For example, $1 and $2 variable are used to read first and second command line arguments. Create a file named “argument.sh” and add the following script. Two argument values read by the following script and prints the total number of arguments and the argument values as output. Bash Scripting Get Arguments from Command Line

echo "Total arguments : $#"
recho "1st argument = $1"
echo "2nd Argument = $2"
echo "3rd argument = $3"
echo "4th Argument = $4"
echo "5th argument = $5"
echo "6th Argument = $6"
echo "7th argument = $7"
echo "8th Argument = $8"
echo "9th argument = $9"

Run the file with bash command.


Reading arguments by getopts function

Create a bash file and add the following script to understand the use of getopts function. ‘getopts’ function is used with while loop to read command line argument options and argument values. Here, 4 options are used which are ‘i’, ‘n’, ‘m’ and ‘e’. case statement is used to match the particular option and store the argument value in a variable. Finally, print the values of the variable.

while getopts ":i:n:m:e:" arg;
case $arg in
n) Name=$OPTARG;;
m) Manufacturing_data=$OPTARG;;
e) Expire_data=$OPTARG;;
echo -e "\n$ID $Name $Manufacturing_data $Expire_data\n"

Run the file with bash command.


bash arg2.sh -i pOO1 -n 'Fafda n Jalebi' -m '05-02-2000' -e '05-02-2025'

Taking filename as argument

Create a bash file and add the following code to count the total number of characters of any file. Here, filename will be passed as command line argument.


totalchar=`wc -c $filename`
echo "Total number of characters are $totalchar"

Run the bash script with the filename as single argument value and run another command to check the total number of characters of that file. Here, student.txt file is used as argument value. Total number of characters of student.txt file is 100p>

Run the file with bash command.

bash arg1.sh student.txt 

wc -c student.txt

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