I am writing a simple function for my program in C that will print a usage statement and exit the program if called. I want to have the option to pass a string as the argument and have it displayed, but also to pass nothing and skip the line. My code is as follows with an example main function:
#include <stdlib.h>
#include <stdio.h>
typedef struct opt_info
{
char *start_path; /* Path to directory to start find in */
int name_flag; /* flag for the name argument */
int type_flag; /* flag for the type argument */
} opt_info;
/* function declarations */
int process_args( opt_info *opts, int ac, char *av[] );
void init_params( opt_info *opts );
void print_usage();
int main ( int ac, char *av[] )
{
opt_info opts; /* struct to store run options */
process_args( &opts, ac, av ); /* handle the argument processing */
printf("%s\n", opts.start_path);
return 0;
}
int process_args( opt_info *opts, int ac, char* av[] )
{
if ( ac < 2 ) /* not enough args */
print_usage();
init_params( opts ); /* initialize opts */
opts->start_path = av[1]; /* store path */
return 0;
}
void init_params( opt_info *opts )
{
opts->name_flag = opts->type_flag = 0; /* set type flags to 0 */
}
void print_usage( char *message )
{
if( message != NULL ) /* check for empty message string */
printf( "%s\n", message );
printf( "USAGE: pfind starting_path [-name filename-or-pattern] " );
printf( "[-type {f|d|b|c|p|l|s}]\n" );
exit( 1 );
}
When I compile with gcc and run the function without passing an argument (i.e. calling print_usage();) the if statement still evaluates as true and I get a line printed out with some garbage data before the "USAGE:..." is printed.
Is there something about C pointers I am missing here, and is there a better way to have this functionality?
edit: updated code to have same function calls as the code I'm having issues with, as requested. The strange thing is when I took away some of the unnecessary code (such as the call to process_args()) I did end up with a compiler warning, but this compiles on my system fine.
