---
name: "strtok"
section: "3"
platform: "macos"
package: "Libc"
version: "1752.120.2"
release: "macOS 26.5"
platforms: ["linux", "freebsd", "macos"]
url: "https://new.carta.tech/strtok"
---

# strtok(3)

string tokens

## NAME

**strtok**, **strtok\_r** – string tokens

## LIBRARY

Standard C Library (libc, -lc)

## SYNOPSIS

**#include \<string.h\>**

*char* *\**\

**strtok**(*char \*restrict str*, *const char \*restrict sep*);

*char* *\**\

**strtok\_r**(*char \*restrict str*, *const char \*restrict sep*, *char \*\*restrict lasts*);

## DESCRIPTION

This interface is obsoleted by [strsep(3)](/strsep/3.md).

The **strtok**() function is used to isolate sequential tokens in a null-terminated string, *str*. These tokens are separated in the string by at least one of the characters in *sep*. The first time that **strtok**() is called, *str* should be specified; subsequent calls, wishing to obtain further tokens from the same string, should pass a null pointer instead. The separator string, *sep*, must be supplied each time, and may change between calls.

The implementation will behave as if no library function calls **strtok**().

The **strtok\_r**() function is a reentrant version of **strtok**(). The context pointer *last* must be provided on each call. The **strtok\_r**() function may also be used to nest two parsing loops within one another, as long as separate context pointers are used.

## RETURN VALUES

The **strtok**() and **strtok\_r**() functions return a pointer to the beginning of each subsequent token in the string, after replacing the token itself with a NUL character. When no more tokens remain, a null pointer is returned.

## EXAMPLES

The following uses **strtok\_r**() to parse two strings using separate contexts:

```
char test[80], blah[80];
char *sep = "\\/:;=-";
char *word, *phrase, *brkt, *brkb;
strcpy(test, "This;is.a:test:of=the/string\\tokenizer-function.");
for (word = strtok_r(test, sep, &brkt);
     word;
     word = strtok_r(NULL, sep, &brkt))
{
    strcpy(blah, "blah:blat:blab:blag");
    for (phrase = strtok_r(blah, sep, &brkb);
         phrase;
         phrase = strtok_r(NULL, sep, &brkb))
    {
        printf("So far we're at %s:%s\n", word, phrase);
    }
}
```

## SEE ALSO

[memchr(3)](/memchr/3.md), [strchr(3)](/strchr/3.md), [strcspn(3)](/strcspn/3.md), [strpbrk(3)](/strpbrk/3.md), [strrchr(3)](/strrchr/3.md), [strsep(3)](/strsep/3.md), [strspn(3)](/strspn/3.md), [strstr(3)](/strstr/3.md), [wcstok(3)](/wcstok/3.md)

## STANDARDS

The **strtok**() function conforms to ISO/IEC 9899:1990 (“ISO C90”). The **strtok\_r**() function conforms to IEEE Std 1003.1-2001 (“POSIX.1”).

## AUTHORS

Wes Peters ⟨*wes@softweyr.com*⟩, Softweyr LLC

Based on the FreeBSD 3.0 implementation.

## BUGS

The System V **strtok**(), if handed a string containing only delimiter characters, will not alter the next starting point, so that a call to **strtok**() with a different (or empty) delimiter string may return a non-NULL value. Since this implementation always alters the next starting point, such a sequence of calls would always return NULL.