– kashyap Apr 24 '17 at 21:57 @kashyap case doesn't loop. Here’s how to call a function in Bash, with or without arguments. Function has to be defined in the shell script first, before you can use it. Imagine you are trying to write a function to compare two integers but these integers will be provided by end user as command line argument; So how will function access these integer values for comparison? Create a bash file and add the following script to understand the use of getopts function. Put any parameters for a bash function right after the function’s name, separated by whitespace, just like you were invoking any shell script or command. When I do to call the function I just need to pass the values that I want for $1 $2 and so forth. You don’t put parentheses around the arguments like you might expect from some programming languages. To do the same without quotes, they'd do program -p hello_world -tSu, where the function program itself gets three arguments. This is a while loop that uses the getopts function and a so-called optstring—in this case u:d:p:f:—to iterate through the arguments. So now about arguments with bash functions. The function badUsage may or may not make an argument. $1 only contains one of them, in both Bash and Zsh. Arguments could be passed to functions and accessed inside the function as $1, $2 etc. The $@ variable expands to all command-line parameters separated by spaces. Here is an example. Bash Functions – In this Bash Tutorial, we shall learn about functions in Bash Shell Scripting with the help of syntax and examples.. About Bash Functions. Don’t … ‘getopts’ function is used with while loop to read command line argument options and argument values. abc "$@" When using $@, you should (almost) always put it in double-quotes to avoid misparsing of arguments containing spaces or wildcards (see below).This works for multiple arguments. Note: for arguments more than 9 $10 won't work (bash will read it as $10), you need to do ${10}, ${11} and so on. It is also portable to all POSIX-compliant shells. Call bash function with arguments. The scope of a local variable limited to function while you can access global variables out of function. badUsage "Option/command not recognized." To pass all the arguments on, you have to use $@. Bash Functions. Each bash function has its own set of positioned arguments just like that of the main script file. 2 - Arguments in bash functions. (Or if you want to lock yourself to exactly three arguments, $1 to $3.) Passing Arguments in Bash Functions. after having the functions above the case it worked, but if I give the two options at a time only the first option is working!!! If you don't modify the argument in any way, there is no need to copy it to a local variable - simply echo "Hello, $1". You should use getopt or getopts for processing options. case statement is used … In the subscripts or functions, the $1 and $2 will represent the parameters, passed to the functions, as internal (local) variables for this subscripts. Here, 4 options are used which are ‘i’, ‘n’, ‘m’ and ‘e’ . badUsage Then there is the function for … We also have an option to pass input arguments to the bash function. You can pass arguments to the bash function easily by writing them with double quotes after function name separated by space. Why would you need that you ask? If an argument is passed to the function, it is printed as a message. You can use $1, $2, $3 and so on to access the arguments inside the function. 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