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What is the purpose of Optind and Optopt?

What is the purpose of Optind and Optopt?

optind is the index of the next element of the argument list to be process, and optopt is the command line option last matched.

What is getopt used for?

getopt is a C library function used to parse command-line options of the Unix/POSIX style. It is a part of the POSIX specification, and is universal to Unix-like systems. It is also the name of a Unix program for parsing command line arguments in shell scripts.

Where is getopt defined?

DESCRIPTION. The getopt() function is a command-line parser that shall follow Utility Syntax Guidelines 3, 4, 5, 6, 7, 9, and 10 in the Base Definitions volume of IEEE Std 1003.1-2001, Section 12.2, Utility Syntax Guidelines.

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What is Getopts in Unix?

getopts is a built-in Unix shell command for parsing command-line arguments. It is designed to process command line arguments that follow the POSIX Utility Syntax Guidelines, based on the C interface of getopt. The predecessor to getopts was the external program getopt by Unix System Laboratories.

Where is Optind defined?

The variable optind is the index of the next element to be processed in argv. The system initializes this value to 1.

What is Optind in getopt?

The variable optind is the index of the next element of argv to be processed. It is initialized to 1, and getopt() updates it as it processes each element of argv[]. The getopt() function returns the next option character (if one is found) from argv that matches a character in optstring, if any.

Is getopts portable?

I know that getopts would be the preferred way in terms of portability but AFAIK it doesn’t support long options. getopt supports long options but the BashGuide recommends strongly against it: Never use getopt(1). getopt cannot handle empty arguments strings, or arguments with embedded whitespace.

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How do you use Getops?

An example of how to use getopts in bash

  1. getopt here to get the input arguments.
  2. check that -s exists, if not return an error.
  3. check that the value after the -s is 45 or 90.
  4. check that the -p exists and there is an input string after.
  5. if the user enters ./myscript -h or just ./myscript then display help.

What is shift in shell script?

Shift is a builtin command in bash which after getting executed, shifts/move the command line arguments to one position left. The first argument is lost after using shift command. This command takes only one integer as an argument.

Should I use getopts?