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Full Discussion: trouble understanding file option and command line arguments
Homework and Emergencies Homework & Coursework Questions trouble understanding file option and command line arguments Post 302558629 by heywoodfloyd on Saturday 24th of September 2011 03:01:08 PM
Old 09-24-2011
trouble understanding file option and command line arguments
Hi,

I am creating a program with the C language that simulates the WC command in Unix. My program needs to count lines, bytes and words. I have not added the code to count bytes and words yet. I am having trouble understanding what the file option/flag '-' does. I can not visualize how it moves through program code. argc and argv look at one line at a time and they only look at what is on the command line. I am not sure how a program is broken up into files for WC to read.

this is the code I have so far:

Code:
/* wc simulate */

#include <stdio.h>
#include <stdlib.h>

char *pgmname; /* name of this program */

int line_count = 0;
int word_count = 0;
int byte_count = 0;

FILE *fp;

void main(argc, argv)

int argc; char *argv[];
{


int i; 
char *cp;

pgmname = argv[0];
fp = stdin;

for(i = 1; i < argc; i++) {
        cp = argv[i];
        if(*cp == '-'){
                if(*++cp == '\n'){
                        line_count++;}
                
                
        }

        else {
                  if(fp != stdin) {
                   fprintf(stderr, "%s: too many arguments\n", pgmname);
                   exit(1);
                }

                fp = fopen(cp, "r")
                if(fp == NULL) {             
                   fprintf(stderr, "%s: unable to read %s\n", pgmname, cp);
                   exit(1);
                }

        }

                printf("%d\n", line_count);
}

                

}

Right now I have code to just count the lines. I am testing the program on a hello world program below:

Code:
#include <stdio.h>

main()
{
printf("Hello World!\n");
}

when I test the program, I get 0 for line count.

California State University, Northridge, USA, Prof Gabrovsky, Comp 322
 

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LEARN ABOUT HPUX

wc

wc(1)							      General Commands Manual							     wc(1)

NAME

       wc - count words, lines, and bytes or characters in a file

SYNOPSIS

       [file]...

DESCRIPTION

       The  command  counts lines, words, and bytes or characters in the named files, or in the standard input if no file names are specified.	It
       also keeps a total count for all named files.

       A word is a string of characters delimited by spaces, tabs, or newlines.

   Options
       recognizes the following options:

	      Report the number of bytes in each input file.

	      Report the number of newline characters in each input file.

	      Report the number of characters in each input file.

	      Report the number of words in each input file.

       The and options are mutually exclusive.	Otherwise, the and or options can be used in any combination to specify that a	subset	of  lines,
       words, and bytes or characters are to be reported.

       When any option is specified, reports only the information requested.  If no option is specified, the default output is

       When a file is specified on the command line, its name is printed along with the counts.

   Standard Output
       By default, the standard output contains an entry for each input file in the form:

	      newlines words bytes file

       If the option is specified, the number of characters replaces the bytes field in this format.

       If any option is specified, the fields for the unspecified options are omitted.

       If no file operand is specified, neither the file name nor the preceding blank character is written.

       If  more than one file operand is specified, an additional line is written at the end of the output, of the same format as the other lines,
       except that the word (in the POSIX locale) is written instead of a file name and the total of each column is written as appropriate.

       Under UNIX Standard environment, a word is a string of characters delimited by spaces, tabs, newline,  carriage-return,	vertical  tab,	or
       form-feed.

RETURN VALUE

       exits with one of the following values:

	      Successful completion.
	      An error occurred.

EXTERNAL INFLUENCES

       For information about the UNIX Standard environment, see standards(5).

   Environment Variables
       determines the range of graphics and space characters, and the interpretation of text as single- and/or multibyte characters.

       determines the language in which messages are displayed.

       If or is not specified in the environment or is null, they default to the value of

       If is not specified or is null, it defaults to (see lang(5)).

       If any internationalization variable contains an invalid setting, they all default to See environ(5).

   International Code Set Support
       Single- and multibyte character code sets are supported.  with a newline character, the count will be off by one.

WARNINGS

       The  command counts the number of newlines to determine the line count.	If a text file has a final line that is not terminated with a new-
       line character, the count will be off by one.

EXAMPLES

       Print the number of words and characters in

       The following is printed when the above command is executed:

       where words is the number of words and chars is the number of characters in

SEE ALSO

       standards(5).

STANDARDS CONFORMANCE

																	     wc(1)
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