So basically, I'm trying to read a file and see if any of the lines matches with a given string in a child process that I've created. The answer is then transmitted to the parent process that prints it out. My problem is that my code only works if I input the last line in my txt file. Any other line is reported as not being present in the file.
#include<stdio.h>
#include<stdlib.h>
#include<sys/types.h>
#include<sys/stat.h>
#include<unistd.h>
#include<string.h>
void Login()
{
char name[20];
int pfd[2];
pid_t pid;
pipe(pfd);
if((pid=fork()) == -1)
{
exit(1);
}
if (pid==0)
{
close(pfd[0]);
FILE *fp = fopen("loginuser.txt", "r");
printf("name:");
scanf("%s", name);
int ok = 0;
if (fp!=NULL)
{
char line[20];
while (fgets(line,20,fp) !=NULL)
{
if (strcmp(name,line)==0) ok = 1;
}
fclose(fp);
}
char s1[]="logged in!";
char s2[]="Not found!";
if(ok==1) write (pfd[1],s1,strlen(s1));
else write(pfd[1],s2,strlen(s2));
exit(0);
}
else
{
close(pfd[1]);
int n;
char reada[20];
n=read (pfd[0],reada,sizeof(reada));
printf("%s",reada);
}
}
int main (int argc, char *argv[])
{
Login();
return 0;
}
loginuser.txt
aaabs
fas
ttt
aloo
Inputing anything other than aloo ,in this case, won't give the correct result. I also have two extra characters after the parent prints something. Any ideea what I've done wrong and why it's not working as intended ?
Fgets return the endtrail caracter in your line, meaning that you were actually comparing aaabs to aaabs\n, thus failing strcmp. If you do this instead :
while (fgets(line,20,fp) !=NULL)
{
size_t i = strlen(line) - 1;
if (line[i] == '\n')
line[i] = '\0';
if (strcmp(name,line)==0)ok = 1;
}
It'll remove each '\n' with a '\0' instead, cleaning your buffer from endlines.
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