Read from a text file and parse lines into words in C -

i'm beginner in c , system programming. homework assignment, need write program reads input stdin parsing lines words , sending words sort sub-processes using system v message queues (e.g., count words). got stuck @ input part. i'm trying process input, remove non-alpha characters, put alpha words in lower case , lastly, split line of words multiple words. far can print alpha words in lower case, there lines between words, believe isn't correct. can take , give me suggestions?

example text file: project gutenberg ebook of iliad of homer, homer

i think correct output should be:

the project gutenberg ebook of iliad of homer homer 

but output following:

project gutenberg ebook of iliad of homer                          <------there line there homer 

i think empty line caused space between "," , "by". tried things "if isspace(c) nothing", doesn't work. code below. or suggestion appreciated.

#include <stdio.h> #include <stdlib.h> #include <ctype.h> #include <fcntl.h> #include <errno.h> #include <unistd.h> #include <string.h>   //main function int main (int argc, char **argv) {     int c;     char *input = argv[1];     file *input_file;      input_file = fopen(input, "r");      if (input_file == 0)     {         //fopen returns 0, null pointer, on failure         perror("canot open input file\n");         exit(-1);     }     else     {                 while ((c =fgetc(input_file)) != eof )         {             //if it's alpha, convert lower case             if (isalpha(c))             {                 c = tolower(c);                 putchar(c);             }             else if (isspace(c))             {                 ;   //do nothing             }             else             {                 c = '\n';                 putchar(c);             }         }     }      fclose(input_file);      printf("\n");      return 0; } 

edit **

i edited code , got correct output:

int main (int argc, char **argv) {     int c;     char *input = argv[1];     file *input_file;      input_file = fopen(input, "r");      if (input_file == 0)     {         //fopen returns 0, null pointer, on failure         perror("canot open input file\n");         exit(-1);     }     else     {         int found_word = 0;          while ((c =fgetc(input_file)) != eof )         {             //if it's alpha, convert lower case             if (isalpha(c))             {                 found_word = 1;                 c = tolower(c);                 putchar(c);             }             else {                 if (found_word) {                     putchar('\n');                     found_word=0;                 }             }          }     }      fclose(input_file);      printf("\n");      return 0; } 

i think need ignore non-alpha character !isalpha(c) otherwise convert lowercase. need keep track when find word in case.

int found_word = 0;  while ((c =fgetc(input_file)) != eof ) {     if (!isalpha(c))     {         if (found_word) {             putchar('\n');             found_word = 0;         }     }     else {         found_word = 1;         c = tolower(c);         putchar(c);     } } 

if need handle apostrophes within words such "isn't" should it.

int found_word = 0; int found_apostrophe = 0;     while ((c =fgetc(input_file)) != eof )     {     if (!isalpha(c))     {         if (found_word) {             if (!found_apostrophe && c=='\'') {                 found_apostrophe = 1;             }             else {                 found_apostrophe = 0;                 putchar('\n');                 found_word = 0;             }                 }     }     else {         if (found_apostrophe) {             putchar('\'');             found_apostrophe == 0;         }         found_word = 1;         c = tolower(c);         putchar(c);     } }