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

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GFS_PIO_GETS(3) 														   GFS_PIO_GETS(3)

NAME
gfs_pio_gets - read one line SYNOPSIS
#include <gfarm/gfarm.h> char *gfs_pio_gets (GFS_File f, char * s, size_t size); DESCRIPTION
gfs_pio_gets() reads one line from the file specified by the parameter gf to the buffer specified by the parameter s. You need to specify the size of the buffer by the parameter size. Unlike gfs_pio_getline(3), this function doesn't remove newline character at the end of the buffer. But if whole contents of the line can- not be stored to the buffer due to its length, or if the file reaches the end without newline, there will be no newline at the end of the buffer. In any case, one '' character is appended to the end of the buffer. If the file reaches its end, the length of the string in the buffer becomes 0. RETURN VALUES
NULL The function terminated successfully. GFARM_ERR_NO_MEMORY Insufficient memory was available. Others An error except the above occurred. The reason is shown by its pointed strings. EXAMPLES
EXAMPLE OF GFS_PIO_GETS FUNCTION #include <stdio.h> #include <stdlib.h> #include <gfarm/gfarm.h> int main(int argc, char **argv) { char *e; GFS_File gf; char buffer[512]; e = gfarm_initialize(&argc, &argv); if (e != NULL) { fprintf(stderr, "gfarm_initialize: %s ", e); return (EXIT_FAILURE); } if (argc <= 1) { fprintf(stderr, "missing gfarm filename "); return (EXIT_FAILURE); } e = gfs_pio_open(argv[1], GFARM_FILE_RDONLY, &gf); if (e != NULL) { fprintf(stderr, "%s: %s ", argv[1], e); return (EXIT_FAILURE); } e = gfs_pio_set_view_global(gf, 0); if (e != NULL) { fprintf(stderr, "%s: gfs_pio_set_view_global: %s ", argv[1], e); return (EXIT_FAILURE); } while ((e = gfs_pio_gets(gf, buffer, sizeof buffer)) != NULL && *buffer != '') { printf("got: %s", buffer); } if (e != NULL) { fprintf(stderr, "ERROR: %s ", e); return (EXIT_FAILURE); } e = gfs_pio_close(gf); if (e != NULL) { fprintf(stderr, "gfs_pio_close: %s ", e); return (EXIT_FAILURE); } e = gfarm_terminate(); if (e != NULL) { fprintf(stderr, "gfarm_initialize: %s ", e); return (EXIT_FAILURE); } return (EXIT_SUCCESS); } SEE ALSO
gfs_pio_open(3), gfs_pio_getline(3), gfs_pio_readline(3), gfs_pio_readdelim(3) Gfarm 13 May 2004 GFS_PIO_GETS(3)
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