File Handling prog explanation

[suvojit168]

Hi all
I was trying to understand file handling in Cpp. I came accross the followig code:

#include <stdio.h>
#include <stdlib.h>
int main(int argc, char *argv[])
{
FILE *fp;
char ch;
if(argc!=2) {
printf("You forgot to enter the filename.\n");
exit(1);
}
if((fp=fopen(argv[1], "r"))==NULL) {
printf("Cannot open file.\n");
exit(1);
}
ch = getc(fp); /* read one character */
while (ch!=EOF) {
putchar(ch); /* print on screen */
ch = getc(fp);
}
fclose(fp);
return 0;
}

Overall prog is clear to me but i dont understand following:

int main(int argc, char *argv[])

I have never seen main in this form. can anyone explain me the parameters and their purpose?

if(argc!=2) {
printf("You forgot to enter the filename.\n");
exit(1);
}

What is happening in the above code snippet?

thanks in advance for replies.....
Regards

[Gumbercules]

argc is the number of cstrings, and argv is the array of cstrings. The first cstring will always be full path of the file "c:\..." , that's why it checks for argc!=2. It gets the parameters when you run it through the console and type something after it, like "myProgram.exe filename".

[suvojit168]

thanks
just one more thing to clarify my doubt: will argv[1] be storing the file name supplied at run time...?

[Gumbercules]

argv[0] would