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:
Right now I have code to just count the lines. I am testing the program on a hello world program below:
when I test the program, I get 0 for line count.
California State University, Northridge, USA, Prof Gabrovsky, Comp 322
Couple of questions as I try to decipher someones code who left...
What would something coded like this do?
IFS=:
grep FIELD1 /Path/Path2/Param.fle | read LBL1 LBL2 USRID EADR SUBJ SERVERNAME CFGTBL DIR
ERR=0
Param.fle contents..
FIELD1:FEI::FIELD2:dATAFIELD BATCH:MAIN SERVER......etc.. (2 Replies)
hi, can someone how to accept command line arguments as a variable using in script?
like: ./scriptname arguments
by accept arguments, I can use it in my script?
thx! (1 Reply)
Sometimes it works for me and sometimes I get this error:
syntax error on line 1, teletype
Basically I've got no idea whats going on, especially at the end of the command: bc
Any help is appreciated (1 Reply)
I have a C++ program. I read command line arguments, but if the value is not supplied, I default or make a calculation. Let's say I set it to a default value.
I can code this in several ways. Here I show three ways. What would be the best way for maintaining this code? The program will get very... (2 Replies)
What are the commands to manage ports from my command line.
Example:
Opening Ports, Closing Ports, Viewing their status, etc.
I am having a hard time finding this answer. I'm trying to trouble shoot some networking problems and it would be very helpful if I could just do this from the... (1 Reply)
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:
1) The script is executed in the Korn shell.
2) Name the shell script file is asg6s.
3) The asg6s file is... (7 Replies)
:wall:killall -wHi
i need to understand how the -w option works in terms of processes.
If this command is issued does it literally terminate all running processes ..wait for them all to be terminated and then return to standard output ?
Thanks in advance (2 Replies)
I am looking for help in processing of those options: '-n' or '-p'
I understand what they do and how to use them.
But, I would like to use them with more than one file (and without any shell-loop; loading the 'perl' once.)
I did try it and -n works on 2 files.
Question is:
- is it possible to... (6 Replies)
Ok, thank you. Again I'm new to the programming thing, I'm just trying to figure out what exactly it is I need to do. How would I cash out bits? Numerous questions. I'm a dreamer. AI attempts to communicate with me regularly especially through unfinished apps that I'm assuming is my responsibility... (1 Reply)
Discussion started by: C-lo
1 Replies
LEARN ABOUT ULTRIX
getopt
getopt(3) Library Functions Manual getopt(3)Name
getopt - get option letter from argument vector
Syntax
#include <stdio.h>
int getopt (argc, argv, optstring)
int argc;
char **argv;
char *optstring;
extern char *optarg;
extern int optind, opterr;
Description
The subroutine returns the next option letter in argv that matches a letter in optstring. The optstring is a string of recognized option
letters; if a letter is followed by a colon, the option is expected to have an argument that may or may not be separated from it by white
space. The optarg is set to point to the start of the option argument on return from
The function places in optind the argv index of the next argument to be processed. The external variable optind is automatically initial-
ized to 1 before the first call to
When all options have been processed (that is, up to the first non-option argument), returns EOF. The special option -- may be used to
delimit the end of the options; EOF will be returned, and -- will be skipped.
Diagnostics
The function prints an error message on stderr and returns a question mark (?) when it encounters an option letter that is not included in
optstring. Setting opterr to 0 disables this error message.
Examples
The following code fragment shows how one might process the arguments for a command that can take the mutually exclusive options a and b,
and the options f and o, both of which require arguments:
#include <stdio.h>
main (argc, argv)
int argc;
char **argv;
{
int c;
extern int optind, opterr;
extern char *optarg;
.
.
.
.
while ((c = getopt (argc, argv, "abf:o:")) != EOF)
switch (c) {
case 'a':
if (bflg)
errflg++;
else
aflg++;
break;
case 'b':
if (aflg)
errflg++;
else
bproc( );
break;
case 'f':
ifile = optarg;
break;
case 'o':
ofile = optarg;
bufsiza = 512;
break;
case '?':
errflg++;
}
if (errflg) {
fprintf (stderr, "usage: . . . ");
exit (2);
}
for ( ; optind < argc; optind++) {
if (access (argv[optind], 4)) {
.
.
.
}
See Alsogetopt(1)getopt(3)