How do I copy or rewind *argv[] Post: 302543305

Sponsored Content

Top Forums Programming How do I copy or rewind *argv[] Post 302543305 by agama on Saturday 30th of July 2011 10:07:54 PM

07-30-2011

Registered User

Here's a small programme that will search through all command line parameters and print each out. It will also scan each parameter and print whether or not it contains all digits (leading whitespace is discarded such that " 123" is considered all digits. It should illustrate how to know when to stop processing command line arguments.

Code:

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

/* return true if string contains all digits
   skips leading whitespace if skip_lws is !0
*/
int all_digits( const char *buf, int skip_lws  )
{
    const char  *sp;            /* pointer into buffer */
    int     all_dig = 1;    /* state of string */

    sp = buf;
    if( skip_lws )      /* skip leading whitespace when asked*/
        for( ; *sp && isspace( *sp ); sp++ );

    if( ! *sp )
        return 0;       /* empty string -- return false (no digits) */

    for( ; *sp; sp++ )      /* for each character until \0 */
        if( ! isdigit( *sp ) )  /* return false on first non-digit found */
            return 0;

    return 1;       /* if we finish the loop, we saw all digits */
}

int main (int argc, const char **argv)
{
    int i;

    fprintf( stderr, "there are %d arguments on the command line\n", argc-1 );

    for( i = 1; i < argc; i++ )         /* for each argument */
    {
        fprintf( stderr, "parameter %d = %s\n", i, argv[i] );
        if( all_digits( argv[i], 1 ) )
            fprintf( stderr, "\targument is all digits\n" );
        else
            fprintf( stderr, "\targument is NOT all digits\n" );
    }

    return 0;
}

Arguments from the command line are zero terminated. From the example above the statement for( ; *sp; sp++ ) will stop when the character pointed to by sp is zero. It is the same as using:

Code:

for( ; *sp != 0; sp++ )

So, to answer your question about what *argv[1]+4 will equal when argv[1] is "eric" -- it should be zero.

Quote:

Also what should i equal,
in the code below.

Code:

argd[i-1]

I'm not sure what you are asking here.

agama

View Public Profile for agama

Find all posts by agama

10 More Discussions You Might Find Interesting

1. Programming

argv

I have a program which I wish to modify. It used to be run from the command line, but now I wish to change this so it can be used as a function. The program has complex argument processing so I want to pass my paramters to as if it were being called by the OS as a program. I have tried to...

2. UNIX for Dummies Questions & Answers

What is the function of rewind()?

3. Programming

help for argv argc

Hi C experts, I have the following code for adding command line option for a program int main (argc, argv) int argc; char *argv; { char *mem_type; //memory type char *name; //name of the memory int addr; //address bits int data; ...

4. Programming

Problem with fgets and rewind function ..

Hello Friends, I got stuck with fgets () & rewind() function .. Please need help.. Actually I am doing a like, The function should read lines from a txt file until the function is called.. If the data from the txt file ends then it goes to the top and then again when the function is called...

5. Shell Programming and Scripting

if #argv = (this OR that) then...

this is in one of my scripts... if ($#argv == 0) then echo 'blah bla' exit 0 endif I want it to be something like this... if ($#argv == 0 OR $argv >=3) echo 'blah bla' exit 0 endif so when the arguments are none, or greater than three I want this "if then" to take over. how? I...

6. UNIX for Dummies Questions & Answers

Need help to understand cpio and no rewind tapes

SCO openserver 5r5 I only have this available to me ... To list the files... cpio -itcvB < /dev/nrct0 To copy a file out cpio -icvdBum filename < /dev/nrct0So cpio is to archive or "zip" files up?? and /dev/nrct0 is the tape drive ??? How can i list all the files inside...

7. Programming

ARGV help in C

Hi, Can somehelp help how to list file in a dir?

8. Programming

help with C, argv

when i run my program, i have a parameter, that i want to set the value to another string i am using int main(int argc, char **argv) { char my_str=argv; printf("%s",my_str); return 0; } and i get Segmentation fault ran using ./my_prog /usr/share/dict/words hello1 ...

9. UNIX for Advanced & Expert Users

O argv, argv, wherefore art thou argv?

All of my machines (various open source derivatives on x86 and amd64) store argv above the stack (at a higher memory address). I am curious to learn if any systems store argv below the stack (at a lower memory address). I am particularly interested in proprietary Unices, such as Solaris, HP-UX,...

10. UNIX for Dummies Questions & Answers

ARGV how to use it?

So i am trying to read in file readFile <GivenFile> modFile looking for a regular file under the directories in the GivenFile and print them out is my over all goal. basically I am looking for anything that looks like a directory in the given file and printing it out. Since I am trying to do...

LEARN ABOUT ULTRIX

audgen

audgen(2) System Calls Manual audgen(2)

Name
audgen - generate an audit record

Syntax
audgen(event, tokenp, argv)
int event;
char *tokenp, *argv[];

Description
The system call generates an audit record, which gets placed in the auditlog.

The argument event is an integer indicating the event type of the operation being audited (see ). The value of event must be between
MIN_TRUSTED_EVENT and MIN_TRUSTED_EVENT+N_TRUSTED_EVENTS.

The argument tokenp is a null-terminated array of token types (see ), each of which represents the type of argument referenced by the cor-
responding *argv argument.

The argument argv is a pointer to an array containing the actual arguments or pointers to those arguments that are to be recorded in the
audit record. A pointer to the actual argument is placed in that array when the argument is a string, array, or other variable length
structure. Arguments represented as int's or short's are placed directly in that array. Each member of the array must be word-aligned.
You cannot change the values for the audit_id, uid, ruid, pid, ppid, device, IP address, or hostid (secondary tokens for these values are
available).

Return Values
Upon successful completion, returns a value of 0. Otherwise, it returns a value of -1 and sets the global integer variable errno to indi-
cate the error.

Restrictions
The call is a privileged system call. No record is generated if the specified event is not being audited for the current process. The
maximum number of arguments referenced by argv is AUD_NPARAM (8).

Diagnostics
The system call fails under the following conditions:

[EACCES] The user is not privileged for this operation.

[EINVAL] The value supplied for the event, tokenp, or argv argument is invalid.

audgen(2)

10 More Discussions You Might Find Interesting

1. Programming

argv

Discussion started by: mbb

2. UNIX for Dummies Questions & Answers

What is the function of rewind()?

Discussion started by: tigerkin

3. Programming

help for argv argc

Discussion started by: return_user

4. Programming

Problem with fgets and rewind function ..

Discussion started by: user_prady

5. Shell Programming and Scripting

if #argv = (this OR that) then...

Discussion started by: ajp7701

6. UNIX for Dummies Questions & Answers

Need help to understand cpio and no rewind tapes

Discussion started by: khaos83_2000

7. Programming

ARGV help in C

Discussion started by: Learnerabc

8. Programming

help with C, argv

Discussion started by: omega666

9. UNIX for Advanced & Expert Users

O argv, argv, wherefore art thou argv?

Discussion started by: alister

10. UNIX for Dummies Questions & Answers

ARGV how to use it?

Discussion started by: squidGreen

LEARN ABOUT ULTRIX

audgen