Shell Functions

Defining a Function

myfunc() 
{ 
  <commands> 
}

Returning Results

Option #1 - Set Different Exit Codes

The following function checks to see if a given number is in range.  An optional upper limit may be provided, which, if omitted, defaults to "10". 

rangecheck() 
{ 
    limit=${2:-10}

    if [ "$1" -lt $limit ] 
    then 
        return 0 
    else 
        return 1 
    fi 
} 

Example usage: 

rangecheck 11  # Exit code=1 since 11 is NOT less than 10 (default)

rangecheck 5 8     # Exit code=0 since 5 is less than 8 

Option #2 - Print the Result

Results may be printed to a terminal or to a file: 

userinfo() 
{ 
    printf "%12s: %s\n" \ 
    USER   "${USER:-No value assigned}" \ 
    PWD    "${PWD:-No value assigned}" 
} > ${1:-/dev/fd/1} 

The output goes to the first argument, a file, if specified, or to /dev/fd/1 (stdout) if omitted. 

Option #3 - Place Results in One or More Variables

Recommend to use the convention of using an output variable that is the name of the function name converted to Uppercase and preceded with an underscore. 

max3() 
{ 
    ... <some commands> ...

    _MAX3=<some result> 

    ... 
}