c - Why am I segfaulting? -

i'm new c, attempting read contents of 1 file character character , output them stream. fopen() command commented out receive segfault (core dumped).

i must run command: ./a.out < testwords.in > myout.txt execute file properly.

here have far:

#include  <stdio.h> void main(char *filename[])  {   printf("filename %s.\n",filename[0]);   //get file based on string inputed   file *fp=fopen(filename[0],"r"); //fetches our file read   char ch;   int linecount = 0;   int wordcount = 0;   int charcount = 0;    //failed find/open file. null character.   if (fp == 0) printf("woops! couldn't open file!\n");    //while not @ end of file, grab next char.   else while( (ch=fgetc(fp)) != eof)      {       if (ch == '\n') //on newline       {     //prints (charcount,wordcount)\n linecount:     printf("(%d,%d)%c%d:",charcount,wordcount,ch,linecount);     charcount = 0;     linecount += 1;       }       else printf("%c",ch); //mirrors char.     }   fclose(fp); //closes file (gotta tidy!)  } 

you can't invent way call main. need use 1 of standard ways, this:

int main(int argc, char *argv[]) {     if (argc < 2) {         fprintf(stderr, "missing filename\n");         return -1;     }     file *fp = fopen(argv[1], "r");     // ... } 

and note argv[0] contains program name (if available; if not contains empty string).

your program segfaulted because received int argc argument char *filename[] parameter. if ran program single command line parameter, value passed in first argument have been 2, not valid pointer value. expression filename[0] dereferences address , causes segfault.