std::strspn

C++

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Language support library

Concepts library (C++20)

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Numerics library

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Regular expressions library (C++11)

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Technical Specifications

Strings library

Null-terminated strings

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Classes

basic_string

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Null-terminated byte strings

Functions
Character manipulation
isalnum isalpha islower isupper isdigit isxdigit isblank (C++11)	iscntrl isgraph isspace isprint ispunct tolower toupper
Conversions to numeric formats
atof atoiatolatoll (C++11) strtolstrtoll (C++11)	strtoulstrtoull (C++11) strtofstrtodstrtold (C++11)(C++11) strtoimaxstrtouimax (C++11)(C++11)
String manipulation
strcpy
strncpy
strcat
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String examination
strlen strcmp strncmp strcoll strchr strrchr	strspn strcspn strpbrk strstr strtok
Memory manipulation
memchr
memcmp
memset
memcpy
memmove
Miscellaneous
strerror

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

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

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 byte string pointed to by src

Example

Run this code

#include <cstring>
#include <string>
#include <iostream>

const char *low_alpha = "qwertyuiopasdfghjklzxcvbnm";
int main()
{
    std::string s = "abcde312$#@";

    std::size_t spnsz = std::strspn(s.c_str(), low_alpha);
    std::cout << "After skipping initial lowercase letters from '" << s
              << "'\nThe remainder is '" << s.substr(spnsz) << "'\n";
}

Output:

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

See also

strcspn	returns the length of the maximum initial segment that consists of only the characters not found in another byte string (function)
wcsspn	returns the length of the maximum initial segment that consists of only the wide characters found in another wide string (function)
strpbrk	finds the first location of any character from a set of separators (function)