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Homework and Emergencies Homework & Coursework Questions Understanding Getopts in an otherwise easy assignment Post 302892906 by ByronicX on Saturday 15th of March 2014 04:54:54 PM
Old 03-15-2014
Understanding Getopts in an otherwise easy assignment

Use and complete the template provided. The entire template must be completed. If you don't, your post may be deleted!

1. The problem statement, all variables and given/known data:

In the command line I will be given files or words which will be USER ID's or a file of USER ID's. I am to let the user of the script know when any of these individuals log in. I can do it a certain why, which is unacceptable.

I could do this without the getopts command, instead I would just write to files and grep each line (each line would be a user ID) and finger it to see if they are on or not.

My problem is after looking all over for information on getopts, it's not making sense to me. I've been messing around with this exampe:

Code:
while getopts ":afz" option;
do
    case $option in
        a)
            echo recieved -a
            ;;
        f)
            echo recieved -f
            ;;
        z)
            echo recieved -z
            ;;
        *)
            echo "invalid option -$OPTARG"
            ;;
        esac
    done


2. Relevant commands, code, scripts, algorithms:

Mainly getopts is encouraged to be used.


3. The attempts at a solution (include all code and scripts):

With the getopts I've been messing with, I realize if I type anything but -a, -f, or -z I will get the *) option which is "invalid option". if I type -z -a or -f, it will of course echo the received thing. My problem is how can I make -a -z -f options to see if file is readable, or to see if the user is a valid userid, or to see if they are even on. Basically, I am obviously not putting 2 and 2 together to see how getopt is handy in this case. I'm assuming if i make -z -a or -f various options like I stated, it ought to work, but honestly, I don't know how to do this, very frustrating.

What I'm asking perhaps, is if I can see an example that is related to my issue, and perhaps an explanation to allow me to complete this.

If I could see how this getopts thing is used for such a case, I'm sure I could do it, because I can do it without getopts!

I've been looking at alternative solutions, but due to scoping issues, I see no other option but to write to a file (which is not allowed for this assignment). and parse the file line by line using finger/grep.

4. Complete Name of School (University), City (State), Country, Name of Professor, and Course Number (Link to Course):
USML, St. Louis, Unix Programming, actually this link has it all:
//*******/~antognolij/cs2750.html
replace ******* with umsl.edu
Note: Without school/professor/course information, you will be banned if you post here! You must complete the entire template (not just parts of it).
 

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getoptcvt(1)                                                       User Commands                                                      getoptcvt(1)

NAME
getoptcvt - convert to getopts to parse command options SYNOPSIS
/usr/lib/getoptcvt [-b] filename /usr/lib/getoptcvt DESCRIPTION
/usr/lib/getoptcvt reads the shell script in filename, converts it to use getopts instead of getopt, and writes the results on the standard output. getopts is a built-in Bourne shell command used to parse positional parameters and to check for valid options. See sh(1). It supports all applicable rules of the command syntax standard (see Rules 3-10, intro(1)). It should be used in place of the getopt command. (See the NOTES section below.) The syntax for the shell's built-in getopts command is: getopts optstring name [ argument...] optstring must contain the option letters the command using getopts will recognize; if a letter is followed by a colon (:), the option is expected to have an argument, or group of arguments, which must be separated from it by white space. Each time it is invoked, getopts places the next option in the shell variable name and the index of the next argument to be processed in the shell variable OPTIND. Whenever the shell or a shell script is invoked, OPTIND is initialized to 1. When an option requires an option-argument, getopts places it in the shell variable OPTARG. If an illegal option is encountered, ? will be placed in name. When the end of options is encountered, getopts exits with a non-zero exit status. The special option -- may be used to delimit the end of the options. By default, getopts parses the positional parameters. If extra arguments (argument ...) are given on the getopts command line, getopts parses them instead. So that all new commands will adhere to the command syntax standard described in intro(1), they should use getopts or getopt to parse posi- tional parameters and check for options that are valid for that command (see the NOTES section below). OPTIONS
The following option is supported: -b Makes the converted script portable to earlier releases of the UNIX system. /usr/lib/getoptcvt modifies the shell script in file- name so that when the resulting shell script is executed, it determines at run time whether to invoke getopts or getopt. EXAMPLES
Example 1: Processing the arguments for a command The following fragment of a shell program shows how one might process the arguments for a command that can take the options -a or -b, as well as the option -o, which requires an option-argument: while getopts abo: c do case $c in a | b) FLAG=$c;; o) OARG=$OPTARG;; ?) echo $USAGE exit 2;; esac done shift `expr $OPTIND - 1` Example 2: Equivalent code expressions This code accepts any of the following as equivalent: cmd -a -b -o "xxx z yy" filename cmd -a -b -o "xxx z yy" -filename cmd -ab -o xxx,z,yy filename cmd -ab -o "xxx z yy" filename cmd -o xxx,z,yy b a filename ENVIRONMENT VARIABLES
See environ(5) for descriptions of the following environment variables that affect the execution of getopts: LC_CTYPE, LC_MESSAGES, and NLSPATH. OPTIND This variable is used by getoptcvt as the index of the next argument to be processed. OPTARG This variable is used by getoptcvt to store the argument if an option is using arguments. EXIT STATUS
The following exit values are returned: 0 An option, specified or unspecified by optstring, was found. >0 The end of options was encountered or an error occurred. ATTRIBUTES
See attributes(5) for descriptions of the following attributes: +-----------------------------+-----------------------------+ | ATTRIBUTE TYPE | ATTRIBUTE VALUE | +-----------------------------+-----------------------------+ |Availability |SUNWcsu | +-----------------------------+-----------------------------+ |CSI |enabled | +-----------------------------+-----------------------------+ SEE ALSO
intro(1), getopts(1), sh(1), shell_builtins(1), getopt(3C), attributes(5) DIAGNOSTICS
getopts prints an error message on the standard error when it encounters an option letter not included in optstring. NOTES
Although the following command syntax rule (see intro(1)) relaxations are permitted under the current implementation, they should not be used because they may not be supported in future releases of the system. As in the EXAMPLES section above, -a and -b are options, and the option -o requires an option-argument. The following example violates Rule 5: options with option-arguments must not be grouped with other options: example% cmd -aboxxx filename The following example violates Rule 6: there must be white space after an option that takes an option-argument: example% cmd -ab oxxx filename Changing the value of the shell variable OPTIND or parsing different sets of arguments may lead to unexpected results. SunOS 5.10 7 Jan 2000 getoptcvt(1)
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