From cppreference.com
A null-terminated byte string (NTBS) is a sequence of nonzero bytes followed by a byte with value zero (the terminating null character). Each byte in a byte string encodes one character of some character set. For example, the character array {'\x63','\x61','\x74','\0'} is an NTBS holding the string "cat" in
encoding.
Functions
Character classification Defined in header
checks if a character is alphanumeric
(function)
checks if a character is alphabetic
(function)
checks if a character is lowercase
(function)
checks if a character is an uppercase character
(function)
checks if a character is a digit
(function)
checks if a character is a hexadecimal character
(function)
checks if a character is a control character
(function)
checks if a character is a graphical character
(function)
checks if a character is a space character
(function)
(C99)
checks if a character is a blank character
(function)
checks if a character is a printing character
(function)
checks if a character is a punctuation character
(function)
Character manipulation
converts a character to lowercase
(function)
converts a character to uppercase
(function)
Note: additional functions whose names begin with either to or is, followed by a lowercase letter, may be added to the header
in future and should not be defined by programs that include that header.
ASCII values characters
decimal hexadecimal octal 0–8 \x0–\x8\0–\10control codes (NUL, etc.) ≠0000000000009 \x9\11tab (\t) ≠00≠0≠00000000010–13 \xA–\xD\12–\15whitespaces (\n, \v, \f, \r) ≠00≠000000000014–31 \xE–\x1F\16–\37control codes ≠00000000000032 \x20\40space 0≠0≠0≠00000000033–47 \x21–\x2F\41–\57!"#$%&'()*+,-./0≠000≠0≠000000048–57 \x30–\x39\60–\7101234567890≠000≠00≠0000≠0≠058–64 \x3A–\x40\72–\100:;<=>?@0≠000≠0≠000000065–70 \x41–\x46\101–\106ABCDEF0≠000≠00≠0≠0≠000≠071–90 \x47–\x5A\107–\132GHIJKLMNOP
QRSTUVWXYZ0≠000≠00≠0≠0≠000091–96 \x5B–\x60\133–\140[\]^_`0≠000≠0≠000000097–102 \x61–\x66\141–\146abcdef0≠000≠00≠0≠00≠00≠0103–122 \x67–\x7A\147–\172ghijklmnop
qrstuvwxyz0≠000≠00≠0≠00≠000123–126 \x7B–\x7E\173–\176{|}~0≠000≠0≠0000000127 \x7F\177backspace character (DEL) ≠000000000000 Conversions to and from numeric formats Defined in header
converts a byte string to a floating-point value
(function)
(C99)
converts a byte string to an integer value
(function)
(C99)
converts a byte string to an integer value
(function)
(C99)
converts a byte string to an unsigned integer value
(function)
(C99)(C99)
converts a byte string to a floating-point value
(function)
(C23)(C23)(C23)
converts a floating-point value to a byte string
(function)
Defined in header
(C99)(C99)
converts a byte string to
or
(function)
String manipulation Defined in header
(C11)
copies one string to another
(function)
(C11)
copies a certain amount of characters from one string to another
(function)
(C11)
concatenates two strings
(function)
(C11)
concatenates a certain amount of characters of two strings
(function)
transform a string so that strcmp would produce the same result as strcoll
(function)
(C23)
allocates a copy of a string
(function)
(C23)
allocates a copy of a string of specified size
(function)
String examination Defined in header
(C11)
returns the length of a given string
(function)
compares two strings
(function)
compares a certain amount of characters of two strings
(function)
compares two strings in accordance to the current locale
(function)
finds the first occurrence of a character
(function)
finds the last occurrence of a character
(function)
returns the length of the maximum initial segment that consists
of only the characters found in another byte string
(function)
returns the length of the maximum initial segment that consists
of only the characters not found in another byte string
(function)
finds the first location of any character in one string, in another string
(function)
finds the first occurrence of a substring of characters
(function)
(C11)
finds the next token in a byte string
(function)
Character array manipulation Defined in header
searches an array for the first occurrence of a character
(function)
compares two buffers
(function)
(C23)(C11)
fills a buffer with a character
(function)
(C11)
copies one buffer to another
(function)
(C11)
moves one buffer to another
(function)
(C23)
copies one buffer to another, stopping after the specified delimiter
(function)
Miscellaneous Defined in header
strerrorstrerror_sstrerrorlen_s
(C11)(C11)
returns a text version of a given error code
(function)
References
Extended contentC23 standard (ISO/IEC 9899:2024):
7.4 Character handling <ctype.h> (p: TBD)
7.8 Format conversion of integer types <inttypes.h> (p: TBD)
7.22 General utilities <stdlib.h> (p: TBD)
7.24 String handling <string.h> (p: TBD)
7.31.2 Character handling <ctype.h> (p: TBD)
7.31.5 Format conversion of integer types <inttypes.h> (p: TBD)
7.31.12 General utilities <stdlib.h> (p: TBD)
7.31.13 String handling <string.h> (p: TBD)
K.3.6 General utilities <stdlib.h> (p: TBD)
K.3.7 String handling <string.h> (p: TBD)
C17 standard (ISO/IEC 9899:2018):
7.4 Character handling <ctype.h> (p: TBD)
7.8 Format conversion of integer types <inttypes.h> (p: TBD)
7.22 General utilities <stdlib.h> (p: TBD)
7.24 String handling <string.h> (p: TBD)
7.31.2 Character handling <ctype.h> (p: TBD)
7.31.5 Format conversion of integer types <inttypes.h> (p: TBD)
7.31.12 General utilities <stdlib.h> (p: TBD)
7.31.13 String handling <string.h> (p: TBD)
K.3.6 General utilities <stdlib.h> (p: TBD)
K.3.7 String handling <string.h> (p: TBD)
C11 standard (ISO/IEC 9899:2011):
7.4 Character handling <ctype.h> (p: 200-204)
7.8 Format conversion of integer types <inttypes.h> (p: 217-220)
7.22 General utilities <stdlib.h> (p: 340-360)
7.24 String handling <string.h> (p: 362-372)
7.31.2 Character handling <ctype.h> (p: 455)
7.31.5 Format conversion of integer types <inttypes.h> (p: 455)
7.31.12 General utilities <stdlib.h> (p: 456)
7.31.13 String handling <string.h> (p: 456)
K.3.6 General utilities <stdlib.h> (p: 604-613)
K.3.7 String handling <string.h> (p: 614-623)
C99 standard (ISO/IEC 9899:1999):
7.4 Character handling <ctype.h> (p: 181-185)
7.8 Format conversion of integer types <inttypes.h> (p: 198-201)
7.20 General utilities <stdlib.h> (p: 306-324)
7.21 String handling <string.h> (p: 325-334)
7.26.2 Character handling <ctype.h> (p: 401)
7.26.4 Format conversion of integer types <inttypes.h> (p: 401)
7.26.10 General utilities <stdlib.h> (p: 402)
7.26.11 String handling <string.h> (p: 402)
C89/C90 standard (ISO/IEC 9899:1990):
4.3 CHARACTER HANDLING <ctype.h>
4.10 GENERAL UTILITIES <stdlib.h>
4.11 STRING HANDLING <string.h>
4.13.2 Character handling <ctype.h>
4.13.7 General utilities <stdlib.h>
4.13.8 String handling <string.h>
See also