Question

#include <stdio.h>
#include <stdlib.h>
#include <strings.h>
#include <unistd.h>
#include <pthread.h>

pthread_mutex_t mtx; // used by each of the three threads to prevent other threads from accessing global_sum during their additions

int global_sum = 0;
typedef struct{
char* word;
char* filename;
}MyStruct;

void *count(void*str)
{
MyStruct *struc;
struc = (MyStruct*)str;
const char *myfile = struc->filename;

FILE *f;
int count=0, j;
char buf[50], read[100];
// myfile[strlen(myfile)-1]='\0';
if(!(f=fopen(myfile,"rt"))){
printf("Wrong file name");
}
else
printf("File opened successfully\n");
for(j=0; fgets(read, 10, f)!=NULL; j++){
if (strcmp(read[j],struc->word)==0)
count++;
}

Need help understanding the if else statement in this program.

Answer 1

The if-else condition is there to check if the file opens successfully or not. The if case is when the file failed to open. In this case, the function fopen() returns NULL. So,

!(f=fopen(myfile,"rt"))

!NULL

true

So, in case file is not opened, the if block is executed which prints

Wrong file name

This occurs in case there is no such file with that given name.

And if the file opens successfull, then the else block executes and the program prints

File opened successfully