After using strtok then using strcmp to compare string is always false

Question

I am new to c, and when reading from stdin I need to separate the words if there is a space. When I type exit I want to print hi but when I use strcmp it always returns false and doesn't print out hi

#include <stdio.h>
#include <fcntl.h>
#include <unistd.h>
#include <string.h>

#define BUFFSIZE 1024
int main()
{
    int n;
    char buffer [BUFFSIZE];
    int pos =0;
    char * parse ;
    char * buf [BUFFSIZE];
    read (STDIN_FILENO, buffer, BUFFSIZE);
    

    parse = strtok(buffer, " ");
    while (parse != NULL) {
        buf[pos] = parse;
        pos++;
    //printf( "%s\n", parse );
        parse = strtok(NULL, " ");
    }
    for (int i=0; i<pos; i++) {
        if (strcmp(buf[i], "exit") ==0) {
            printf("hi");
        }
        printf("%s\n",buf[i]);
    }
    

} // main

Answer 1

There are several changes you need to make, mostly highlighted in the comments.

1. You need to ensure that the string is null-terminated before you pass it to strtok() .
2. You need to ensure that you split on at least blank and newline, and probably tab and carriage return too.

You should also check that the read() worked and returned data.

Those changes lead to something like this:

#include <stdio.h>
#include <string.h>
#include <unistd.h>

#define BUFFSIZE 1024
#define DELIMITERS " \n\t\r"

int main(void)
{
    char buffer[BUFFSIZE + 1];  /* Allow for a null terminator */
    int pos = 0;
    char *parse;
    char *buf[BUFFSIZE];
    int nbytes = read(STDIN_FILENO, buffer, BUFFSIZE);
    if (nbytes <= 0)
    {
        fprintf(stderr, "Failed to read anything from standard input\n");
        return 1;
    }
    buffer[nbytes] = '\0';

    parse = strtok(buffer, DELIMITERS);
    while (parse != NULL)
    {
        printf("parse [%s]\n", parse);
        buf[pos] = parse;
        pos++;
        parse = strtok(NULL, DELIMITERS);
    }
    printf("pos = %d\n", pos);
    for (int i = 0; i < pos; i++)
    {
        if (strcmp(buf[i], "exit") == 0)
        {
            printf("found '%s' at index %d\n", buf[i], i);
        }
        printf("%s\n", buf[i]);
    }

    return 0;
}

That includes some diagnostic printing. Note that the message hi is singularly uninformative, especially as the message did not end with a newline. End messages with newlines at minimum.

With the more extensive delimiters shown, the output looks like:

parse [exit]
pos = 1
found 'exit' at index 0
exit
``

With just blank as a delimiter, the output looked like:

```none
parse [exit
]
pos = 1
exit

Note the extra blank line after exit .

With a more extensive input string in due course, the keyword exit will be recognized. , the output is:

parse [in]
parse [due]
parse [course,]
parse [the]
parse [keyword]
parse [exit]
parse [will]
parse [be]
parse [recognized.]
pos = 9
in
due
course,
the
keyword
found 'exit' at index 5
exit
will
be
recognized.

You decide if that's satisfactory. I think the loop should probably end when the match is detected.