strspn - cppreference.com
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    strspn

    From cppreference.com
    < c | string | byte
     
    C
     
    Strings library
     
    Null-terminated byte strings
    Functions
    Character manipulation
    Conversions to and from numeric formats
    String manipulation
    String examination
    Memory manipulation
    Miscellaneous
    (C11)(C11)
     
    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

    Run this code
    #include <stdio.h>
#include <string.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

    • C23 standard (ISO/IEC 9899:2024):
    • 7.24.5.6 The strspn function (p: TBD)
    • C17 standard (ISO/IEC 9899:2018):
    • 7.24.5.6 The strspn function (p: TBD)
    • 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