Searching inside text in C

strchr finds a character, strstr a substring, and both return NULL when absent.

#include <string.h>

long index_of(const char *text, char target) {
    const char *found = strchr(text, target);
    return (found == NULL) ? -1 : (long) (found - text);
}

const char *extension_of(const char *path) {
    const char *dot = strrchr(path, '.');
    return (dot == NULL || dot == path) ? "" : dot + 1;
}

int contains(const char *haystack, const char *needle) {
    return strstr(haystack, needle) != NULL;
}

How it works

1. The return value is a pointer into the original string.
2. Subtracting the base gives you the index.
3. strrchr searches from the end, which suits file extensions.

Keywords and builtins used here

• NULL
• char
• const
• contains
• extension_of
• index_of
• int
• long
• return

The run, in numbers

Lines

15

Characters to type

403

Tokens

120

Three-star pace

100 tpm

At the three-star pace of 100 tokens a minute, this run takes about 72 seconds.

Type this snippet

Step 2 of 3 in Comparing & searching, step 6 of 13 in Strings & text.

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