strspn

Defined in header <string.h>
size_t strspn( const char *dest, const char *src );

Returns the length of the maximum initial segment (span) of the null-terminated byte string pointed to by dest, that consists of only the characters found in the null-terminated byte string pointed to by src.

The behavior is undefined if either dest or src is not a pointer to a null-terminated byte string.

Parameters

dest - pointer to the null-terminated byte string to be analyzed
src - pointer to the null-terminated byte string that contains the characters to search for

Return value

The length of the maximum initial segment that contains only characters from the null-terminated byte string pointed to by src.

Example

#include <string.h>
#include <stdio.h>
 
int main(void)
{
    const char *string = "abcde312$#@";
    const char *low_alpha = "qwertyuiopasdfghjklzxcvbnm";
 
    size_t spnsz = strspn(string, low_alpha);
    printf("After skipping initial lowercase letters from '%s'\n"
           "The remainder is '%s'\n", string, string+spnsz);
}

Output:

After skipping initial lowercase letters from 'abcde312$#@'
The remainder is '312$#@'

References

  • C11 standard (ISO/IEC 9899:2011):
    • 7.24.5.6 The strspn function (p: 369)
  • C99 standard (ISO/IEC 9899:1999):
    • 7.21.5.6 The strspn function (p: 332)
  • C89/C90 standard (ISO/IEC 9899:1990):
    • 4.11.5.6 The strspn function

See also

returns the length of the maximum initial segment that consists
of only the characters not found in another byte string
(function)
(C95)
returns the length of the maximum initial segment that consists
of only the wide characters found in another wide string
(function)
finds the first location of any character in one string, in another string
(function)

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