Standard C Library Functions Table, By Name

This table briefly describes the C library functions, listed in alphabetical order. This table provides the include file name and the function prototype for each function.

Table 1. Standard C Library Functions
Function System Include File Function Prototype Description
abort stdlib.h void abort(void); Stops a program abnormally.
abs stdlib.h int abs(int n); Calculates the absolute value of an integer argument n.
acos math.h double acos(double x); Calculates the arc cosine of x.
asctime time.h char *asctime(const struct tm *time); Converts the time that is stored as a structure to a character string.
asctime_r time.h char *asctime_r (const struct tm *tm, char *buf); Converts tm that is stored as a structure to a character string. (Restartable version of asctime.)
asin math.h double asin(double x); Calculates the arc sine of x.
assert assert.h void assert(int expression); Prints a diagnostic message and ends the program if the expression is false.
atan math.h double atan(double x); Calculates the arc tangent of x.
atan2 math.h double atan2(double y, double x); Calculates the arc tangent of y/x.
atexit stdlib.h int atexit(void (*func)(void)); Registers a function to be called at normal termination.
atof stdlib.h double atof(const char *string); Converts string to a double-precision floating-point value.
atoi stdlib.h int atoi(const char *string); Converts string to an integer.
atol stdlib.h long int atol(const char *string); Converts string to a long integer.
bsearch stdlib.h void *bsearch(const void *key, const void *base, size_t num, size_t size, int (*compare) (const void *element1, const void *element2)); Performs a binary search on an array of num elements, each of size bytes. The array must be sorted in ascending order by the function pointed to by compare.
btowc
stdio.h
wchar.h
 wint_t btowc(int c); Determines whether c constitues a valid multibyte character in the initial shift state.
calloc stdlib.h void *calloc(size_t num, size_t size); Reserves storage space for an array of num elements, each of size size, and initializes the values of all elements to 0.
catclose6 nl_types.h int catclose (nl_catd catd); Closes a previously opened message catalog.
catgets6 nl_types.h char *catgets(nl_catd catd, int set_id, int msg_id, const char *s); Retrieves a message from an open message catalog.
catopen6 nl_types.h nl_catd catopen (const char *name, int oflag); Opens a message catalog, which must be done before a message can be retrieved.
ceil math.h double ceil(double x); Calculates the double value representing the smallest integer that is greater than or equal to x.
clearerr stdio.h void clearerr(FILE *stream); Resets the error indicators and the end-of-file indicator for stream.
clock time.h clock_t clock(void); Returns the processor time that has elapsed since the job was started.
cos math.h double cos(double x); Calculates the cosine of x.
cosh math.h double cosh(double x); Calculates the hyperbolic cosine of x.
ctime time.h char *ctime(const time_t *time); Converts time to a character string.
ctime64 time.h char *ctime64(const time64_t *time); Converts time to a character string.
ctime_r time.h char *ctime_r(const time_t *time, char *buf); Converts time to a character string. (Restartable version of ctime.)
ctime64_r time.h char *ctime64_r(const time64_t *time, char *buf); Converts time to a character string. (Restartable version of ctime64.)
difftime time.h double difftime(time_t time2, time_t time1); Computes the difference between time2 and time1.
difftime64 time.h double difftime64(time64_t time2, time64_t time1); Computes the difference between time2 and time1.
div stdlib.h div_t div(int numerator, int denominator); Calculates the quotient and remainder of the division of numerator by denominator.
erf math.h double erf(double x); Calculates the error function of x.
erfc math.h double erfc(double x); Calculates the error function for large values of x.
exit stdlib.h void exit(int status); Ends a program normally.
exp math.h double exp(double x); Calculates the exponential function of a floating-point argument x.
fabs math.h double fabs(double x); Calculates the absolute value of a floating-point argument x.
fclose stdio.h int fclose(FILE *stream); Closes the specified stream.
fdopen5 stdio.h FILE *fdopen(int handle, const char *type); Associates an input or output stream with the file identified by handle.
feof stdio.h int feof(FILE *stream); Tests whether the end-of-file flag is set for a given stream.
ferror stdio.h int ferror(FILE *stream); Tests for an error indicator in reading from or writing to stream.
fflush1 stdio.h int fflush(FILE *stream); Writes the contents of the buffer associated with the output stream.
fgetc1 stdio.h int fgetc(FILE *stream); Reads a single unsigned character from the input stream.
fgetpos1 stdio.h int fgetpos(FILE *stream, fpos_t *pos); Stores the current position of the file pointer associated with stream into the object pointed to by pos.
fgets1 stdio.h char *fgets(char *string, int n, FILE *stream); Reads a string from the input stream.
fgetwc6
stdio.h
wchar.h
 wint_t fgetwc(FILE *stream); Reads the next multibyte character from the input stream pointed to by stream.
fgetws6
stdio.h
wchar.h
 wchar_t *fgetws(wchar_t *wcs, int n, FILE *stream); Reads wide characters from the stream into the array pointed to by wcs.
fileno5 stdio.h int fileno(FILE *stream); Determines the file handle currently associated with stream.
floor math.h double floor(double x); Calculates the floating-point value representing the largest integer less than or equal to x.
fmod math.h double fmod(double x, double y); Calculates the floating-point remainder of x/y.
fopen stdio.h FILE *fopen(const char *filename, const char *mode); Opens the specified file.
fprintf stdio.h int fprintf(FILE *stream, const char *format-string, arg-list); Formats and prints characters and values to the output stream.
fputc1 stdio.h int fputc(int c, FILE *stream); Prints a character to the output stream.
fputs1 stdio.h int fputs(const char *string, FILE *stream); Copies a string to the output stream.
fputwc6
stdio.h
wchar.h
 wint_t fputwc(wchar_t wc, FILE *stream); Converts the wide character wc to a multibyte character and writes it to the output stream pointed to by stream at the current position.
fputws6
stdio.h
wchar.h
 int fputws(const wchar_t *wcs, FILE *stream); Converts the wide-character string wcs to a multibyte-character string and writes it to stream as a multibyte character string.
fread stdio.h size_t fread(void *buffer, size_t size, size_t count, FILE *stream); Reads up to count items of size length from the input stream, and stores them in buffer.
free stdlib.h void free(void *ptr); Frees a block of storage.
freopen stdio.h FILE *freopen(const char *filename, const char *mode, FILE *stream); Closes stream, and reassigns it to the file specified.
frexp math.h double frexp(double x, int *expptr); Separates a floating-point number into its mantissa and exponent.
fscanf stdio.h int fscanf(FILE *stream, const char *format-string, arg-list); Reads data from stream into locations given by arg-list.
fseek1 stdio.h int fseek(FILE *stream, long int offset, int origin); Changes the current file position associated with stream to a new location.
fsetpos1 stdio.h int fsetpos(FILE *stream, const fpos_t *pos); Moves the current file position to a new location determined by pos.
ftell1 stdio.h long int ftell(FILE *stream); Gets the current position of the file pointer.
fwide6
stdio.h
wchar.h
 int fwide(FILE *stream, int mode); Determines the orientation of the stream pointed to by stream.
fwprintf6
stdio.h
wchar.h
 int fwprintf(FILE *stream, const wchar_t *format, arg-list); Writes output to the stream pointed to by stream.
fwrite stdio.h size_t fwrite(const void *buffer, size_t size,size_t count, FILE *stream); Writes up to count items of size length from buffer to stream.
fwscanf6
stdio.h
wchar.h
 int fwscanf(FILE *stream, const wchar_t *format, arg-list) Reads input from the stream pointed to by stream.
gamma math.h double gamma(double x); Computes the Gamma Function
getc1 stdio.h int getc(FILE *stream); Reads a single character from the input stream.
getchar1 stdio.h int getchar(void); Reads a single character from stdin.
getenv stdlib.h char *getenv(const char *varname); Searches environment variables for varname.
gets stdio.h char *gets(char *buffer); Reads a string from stdin, and stores it in buffer.
getwc6
stdio.h
wchar.h
 wint_t getwc(FILE *stream); Reads the next multibyte character from stream, converts it to a wide character and advances the associated file position indicator for stream.
getwchar6 wchar.h wint_t getwchar(void); Reads the next multibyte character from stdin, converts it to a wide character, and advances the associated file position indicator for stdin.
gmtime time.h struct tm *gmtime(const time_t *time); Converts a time value to a structure of type tm.
gmtime64 time.h struct tm *gmtime64(const time64_t *time); Converts a time value to a structure of type tm.
gmtime_r time.h struct tm *gmtime_r (const time_t *time, struct tm *result); Converts a time value to a structure of type tm. (Restartable version of gmtime.)
gmtime64_r time.h struct tm *gmtime64_r (const time64_t *time, struct tm *result); Converts a time value to a structure of type tm. (Restartable version of gmtime64.)
hypot math.h double hypot(double side1, double side2); Calculates the hypotenuse of a right-angled triangle with sides of length side1 and side2.
isalnum ctype.h int isalnum(int c); Tests if c is alphanumeric.
isalpha ctype.h int isalpha(int c); Tests if c is alphabetic.
isascii4 ctype.h int isascii(int c); Tests if c is within the 7-bit US-ASCII range.
isblank ctype.h int isblank(int c); Tests if c is a blank or tab character.
iscntrl ctype.h int iscntrl(int c); Tests if c is a control character.
isdigit ctype.h int isdigit(int c); Tests if c is a decimal digit.
isgraph ctype.h int isgraph(int c); Tests if c is a printable character excluding the space.
islower ctype.h int islower(int c); Tests if c is a lowercase letter.
isprint ctype.h int isprint(int c); Tests if c is a printable character including the space.
ispunct ctype.h int ispunct(int c); Tests if c is a punctuation character.
isspace ctype.h int isspace(int c); Tests if c is a whitespace character.
isupper ctype.h int isupper(int c); Tests if c is an uppercase letter.
iswalnum4 wctype.h int iswalnum (wint_t wc); Checks for any alphanumeric wide character.
iswalpha4 wctype.h int iswalpha (wint_t wc); Checks for any alphabetic wide character.
iswblank4 wctype.h int iswblank (wint_t wc); Checks for any blank or tab wide character.
iswcntrl4 wctype.h int iswcntrl (wint_t wc); Tests for any control wide character.
iswctype4 wctype.h int iswctype(wint_t wc, wctype_t wc_prop); Determines whether or not the wide character wc has the property wc_prop.
iswdigit4 wctype.h int iswdigit (wint_t wc); Checks for any decimal-digit wide character.
iswgraph4 wctype.h int iswgraph (wint_t wc); Checks for any printing wide character except for the wide-character space.
iswlower4 wctype.h int iswlower (wint_t wc); Checks for any lowercase wide character.
iswprint4 wctype.h int iswprint (wint_t wc); Checks for any printing wide character.
iswpunct4 wctype.h int iswpunct (wint_t wc); Test for a wide non-alphanumeric, non-space character.
iswspace4 wctype.h int iswspace (wint_t wc); Checks for any wide character that corresponds to an implementation-defined set of wide characters for which iswalnum is false.
iswupper4 wctype.h int iswupper (wint_t wc); Checks for any uppercase wide character.
iswxdigit4 wctype.h int iswxdigit (wint_t wc); Checks for any hexadecimal digit character.
isxdigit4 wctype.h int isxdigit(int c); Tests if c is a hexadecimal digit.
j0 math.h double j0(double x); Calculates the Bessel function value of the first kind of order 0.
j1 math.h double j1(double x); Calculates the Bessel function value of the first kind of order 1.
jn math.h double jn(int n, double x); Calculates the Bessel function value of the first kind of order n.
labs stdlib.h long int labs(long int n); Calculates the absolute value of n.
ldexp math.h double ldexp(double x, int exp); Returns the value of x multiplied by (2 to the power of exp).
ldiv stdlib.h ldiv_t ldiv(long int numerator, long int denominator); Calculates the quotient and remainder of numerator/denominator.
localeconv locale.h struct lconv *localeconv(void); Formats numeric quantities in struct lconv according to the current locale.
localtime time.h struct tm *localtime(const time_t *timeval); Converts timeval to a structure of type tm.
localtime64 time.h struct tm *localtime64(const time64_t *timeval); Converts timeval to a structure of type tm.
localtime_r time.h struct tm *localtime_r (const time_t *timeval, struct tm *result); Converts a time value to a structure of type tm. (Restartable version of localtime.)
localtime64_r time.h struct tm *localtime64_r (const time64_t *timeval, struct tm *result); Converts a time value to a structure of type tm. (Restartable version of localtime64.)
log math.h double log(double x); Calculates the natural logarithm of x.
log10 math.h double log10(double x); Calculates the base 10 logarithm of x.
longjmp setjmp.h void longjmp(jmp_buf env, int value); Restores a stack environment previously set in env by the setjmp function.
malloc stdlib.h void *malloc(size_t size); Reserves a block of storage.
mblen stdlib.h int mblen(const char *string, size_t n); Determines the length of a multibyte character string.
mbrlen4 wchar.h int mbrlen (const char *s, size_t n, mbstate_t *ps); Determines the length of a multibyte character. (Restartable version of mblen.)
mbrtowc4 wchar.h int mbrtowc (wchar_t *pwc, const char *s, size_t n, mbstate_t *ps); Convert a multibyte character to a wide character (Restartable version of mbtowc.)
mbsinit4 wchar.h int mbsinit (const mbstate_t *ps); Test state object *ps for initial state.
mbsrtowcs4 wchar.h size_t mbsrtowc (wchar_t *dst, const char **src, size_t len, mbstate_t *ps); Convert multibyte string to a wide character string. (Restartable version of mbstowcs.)
mbstowcs stdlib.h size_t mbstowcs(wchar_t *pwc, const char *string, size_t n); Converts the multibyte characters in string to their corresponding wchar_t codes, and stores not more than n codes in pwc.
mbtowc stdlib.h int mbtowc(wchar_t *pwc, const char *string, size_t n); Stores the wchar_t code corresponding to the first n bytes of multibyte character string into the wchar_t character pwc.
memchr string.h void *memchr(const void *buf, int c, size_t count); Searches the first count bytes of buf for the first occurrence of c converted to an unsigned character.
memcmp string.h int memcmp(const void *buf1, const void *buf2, size_t count); Compares up to count bytes of buf1 and buf2.
memcpy string.h void *memcpy(void *dest, const void *src, size_t count); Copies count bytes of src to dest.
memmove string.h void *memmove(void *dest, const void *src, size_t count); Copies count bytes of src to dest. Allows copying between objects that overlap.
memset string.h void *memset(void *dest, int c, size_t count); Sets count bytes of dest to a value c.
mktime time.h time_t mktime(struct tm *time); Converts local time into calendar time.
mktime64 time.h time64_t mktime64(struct tm *time); Converts local time into calendar time.
modf math.h double modf(double x, double *intptr); Breaks down the floating-point value x into fractional and integral parts.
nextafter math.h double nextafter(double x, double y); Calculates the next representable value after x in the direction of y.
nextafterl math.h long double nextafterl(long double x, long double y); Calculates the next representable value after x in the direction of y.
nexttoward math.h double nexttoward(double x, long double y); Calculates the next representable value after x in the direction of y.
nexttowardl math.h long double nexttowardl(long double x, long double y); Calculates the next representable value after x in the direction of y.
nl_langinfo4 langinfo.h char *nl_langinfo(nl_item item); Retrieve from the current locale the string that describes the requested information specified by item.
perror stdio.h void perror(const char *string); Prints an error message to stderr.
pow math.h double pow(double x, double y); Calculates the value x to the power y.
printf stdio.h int printf(const char *format-string, arg-list); Formats and prints characters and values to stdout.
putc1 stdio.h int putc(int c, FILE *stream); Prints c to the output stream.
putchar1 stdio.h int putchar(int c); Prints c to stdout.
putenv stdlib.h int *putenv(const char *varname); Sets the value of an environment variable by altering an existing variable or creating a new one.
puts stdio.h int puts(const char *string); Prints a string to stdout.
putwc6
stdio.h
wchar.h
 wint_t putwchar(wchar_t wc, FILE *stream); Converts the wide character wc to a multibyte character, and writes it to the stream at the current position.
putwchar6 wchar.h wint_t putwchar(wchar_t wc); Converts the wide character wc to a multibyte character and writes it to stdout.
qsort stdlib.h void qsort(void *base, size_t num, size_t width, int(*compare)(const void *element1, const void *element2)); Performs a quick sort of an array of num elements, each of width bytes in size.
quantexpd32 math.h _Decimal32 quantized32(_Decimal32 x, _Decimal32 y); Compute the quantum exponent of a single-precision decimal floating-point value.
quantexpd64 math.h _Decimal64 quantized64(_Decimal64 x, _Decimal64 y); Compute the quantum exponent of a double-precision decimal floating-point value.
quantexpd128 math.h _Decimal128 quantized128(_Decimal128 x, _Decimal128 y); Compute the quantum exponent of a quad-precision decimal floating-point value.
quantized32 math.h int quantexpd32(_Decimal32 x); Set the quantum exponent of a single-precision decimal floating-point value to the quantum exponent of another single-precision decimal floating-point value.
quantized64 math.h int quantexpd64(_Decimal64 x); Set the quantum exponent of a double-precision decimal floating-point value to the quantum exponent of another double-precision decimal floating-point value.
quantized128 math.h int quantexpd128(_Decimal128 x); Set the quantum exponent of a quad-precision decimal floating-point value to the quantum exponent of another quad-precision decimal floating-point value.
samequantumd32 math.h __bool__ samequantumd32(_Decimal32 x, _Decimal32 y); Determine if the quantum exponents of two single-precision decimal floating-point values are the same.
samequantumd64 math.h __bool__ samequantumd64(_Decimal64 x, _Decimal64 y); Determine if the quantum exponents of two double-precision decimal floating-point values are the same.
samequantumd128 math.h __bool__ samequantumd128(_Decimal128 x, _Decimal128 y); Determine if the quantum exponents of two quad-precision decimal floating-point values are the same.
raise signal.h int raise(int sig); Sends the signal sig to the running program.
rand stdlib.h int rand(void); Returns a pseudo-random integer.
rand_r stdlib.h int rand_r(void); Returns a pseudo-random integer. (Restartable version)
realloc stdlib.h void *realloc(void *ptr, size_t size); Changes the size of a previously reserved storage block.
regcomp regex.h int regcomp(regex_t *preg, const char *pattern, int cflags); Compiles the source regular expression pointed to by pattern into an executable version and stores it in the location pointed to by preg.
regerror regex.h size_t regerror(int errcode, const regex_t *preg, char *errbuf, size_t errbuf_size); Finds the description for the error code errcode for the regular expression preg.
regexec regex.h int regexec(const regex_t *preg, const char *string, size_t nmatch, regmatch_t *pmatch, int eflags); Compares the null-ended string string against the compiled regular expression preg to find a match between the two.
regfree regex.h void regfree(regex_t *preg); Frees any memory that was allocated by regcomp to implement the regular expression preg.
remove stdio.h int remove(const char *filename); Deletes the file specified by filename.
rename stdio.h int rename(const char *oldname, const char *newname); Renames the specified file.
rewind1 stdio.h void rewind(FILE *stream); Repositions the file pointer associated with stream to the beginning of the file.
scanf stdio.h int scanf(const char *format-string, arg-list); Reads data from stdin into locations given by arg-list.
setbuf stdio.h void setbuf(FILE *stream, char *buffer); Controls buffering for stream.
setjmp setjmp.h int setjmp(jmp_buf env); Saves a stack environment that can be subsequently restored by longjmp.
setlocale locale.h char *setlocale(int category, const char *locale); Changes or queries variables defined in the locale.
setvbuf stdio.h int setvbuf(FILE *stream, char *buf, int type, size_t size); Controls buffering and buffer size for stream.
signal signal.h void(*signal (int sig, void(*func)(int))) (int); Registers func as a signal handler for the signal sig.
sin math.h double sin(double x); Calculates the sine of x.
sinh math.h double sinh(double x); Calculates the hyperbolic sine of x.
snprintf stdio.h int snprintf(char *outbuf, size_t n, const char*, ...) Same as sprintf except that the function will stop after n characters have been written to outbuf.
sprintf stdio.h int sprintf(char *buffer, const char *format-string, arg-list); Formats and stores characters and values in buffer.
sqrt math.h double sqrt(double x); Calculates the square root of x.
srand stdlib.h void srand(unsigned int seed); Sets the seed for the pseudo-random number generator.
sscanf stdio.h int sscanf(const char *buffer, const char *format, arg-list); Reads data from buffer into the locations given by arg-list.
strcasecmp strings.h int srtcasecmp(const char *string1, const char *string2); Compares strings without case sensitivity.
strcat string.h char *strcat(char *string1, const char *string2); Concatenates string2 to string1.
strchr string.h char *strchr(const char *string, int c); Locates the first occurrence of c in string.
strcmp string.h int strcmp(const char *string1, const char *string2); Compares the value of string1 to string2.
strcoll string.h int strcoll(const char *string1, const char *string2); Compares two strings using the collating sequence in the current locale.
strcpy string.h char *strcpy(char *string1, const char *string2); Copies string2 into string1.
strcspn string.h size_t strcspn(const char *string1, const char *string2); Returns the length of the initial substring of string1 consisting of characters not contained in string2.
strerror string.h char *strerror(int errnum); Maps the error number in errnum to an error message string.
strfmon4 wchar.h int strfmon (char *s, size_t maxsize, const char *format, ...); Converts monetary value to string.
strftime time.h size_t strftime (char *dest, size_t maxsize, const char *format, const struct tm *timeptr); Stores characters in an array pointed to by dest, according to the string determined by format.
strlen string.h size_t strlen(const char *string); Calculates the length of string.
strncasecmp strings.h int strncasecmp(const char *string1, const char *string2, size_t count); Compares strings without case sensitivity.
strncat string.h char *strncat(char *string1, const char *string2, size_t count); Concatenates up to count characters of string2 to string1.
strncmp string.h int strncmp(const char *string1, const char *string2, size_t count); Compares up to count characters of string1 and string2.
strncpy string.h char *strncpy(char *string1, const char *string2, size_t count); Copies up to count characters of string2 to string1.
strpbrk string.h char *strpbrk(const char *string1, const char *string2); Locates the first occurrence in string1 of any character in string2.
strptime4 time.h char *strptime (const char *buf, const char *format, struct tm *tm); Date and time conversion
strrchr string.h char *strrchr(const char *string, int c); Locates the last occurrence of c in string.
strspn string.h size_t strspn(const char *string1, const char *string2); Returns the length of the initial substring of string1 consisting of characters contained in string2.
strstr string.h char *strstr(const char *string1, const char *string2); Returns a pointer to the first occurrence of string2 in string1.
strtod stdlib.h double strtod(const char *nptr, char **endptr); Converts nptr to a double precision value.
strtod32 stdlib.h _Decimal32 strtod32(const char *nptr, char **endptr); Converts nptr to a single-precision decimal floating-point value.
strtod64 stdlib.h _Decimal64 strtod64(const char *nptr, char **endptr); Converts nptr to a double-precision decimal floating-point value.
strtod128 stdlib.h _Decimal128 strtod128(const char *nptr, char **endptr); Converts nptr to a quad-precision decimal floating-point value.
strtof stdlib.h float strtof(const char *nptr, char **endptr); Converts nptr to a float value.
strtok string.h char *strtok(char *string1, const char *string2); Locates the next token in string1 delimited by the next character in string2.
strtok_r string.h char *strtok_r(char *string, const char *seps, char **lasts); Locates the next token in string delimited by the next character in seps. (Restartable version of strtok.)
strtol stdlib.h long int strtol(const char *nptr, char **endptr, int base); Converts nptr to a signed long integer.
strtold stdlib.h long double strtold(const char *nptr, char **endptr); Converts nptr to a long double value.
strtoul stdlib.h unsigned long int strtoul(const char *string1, char **string2, int base); Converts string1 to an unsigned long integer.
strxfrm string.h size_t strxfrm(char *string1, const char *string2, size_t count); Converts string2 and places the result in string1. The conversion is determined by the program's current locale.
swprintf wchar.h int swprintf(wchar_t *wcsbuffer, size_t n, const wchar_t *format, arg-list); Formats and stores a series of wide characters and values into the wide-character buffer wcsbuffer.
swscanf wchar.h int swscanf (const wchar_t *buffer, const wchar_t *format, arg-list) Reads data from buffer into the locations given by arg-list.
system stdlib.h int system(const char *string); Passes string to the system command analyzer.
tan math.h double tan(double x); Calculates the tangent of x.
tanh math.h double tanh(double x); Calculates the hyperbolic tangent of x.
time time.h time_t time(time_t *timeptr); Returns the current calendar time.
time64 time.h time64_t time64(time64_t *timeptr); Returns the current calendar time.
tmpfile stdio.h FILE *tmpfile(void); Creates a temporary binary file and opens it.
tmpnam stdio.h char *tmpnam(char *string); Generates a temporary file name.
toascii ctype.h int toascii(int c); Converts c to a character in the 7-bit US-ASCII character set.
tolower ctype.h int tolower(int c); Converts c to lowercase.
toupper ctype.h int toupper(int c); Converts c to uppercase.
towctrans wctype.h wint_t towctrans(wint_t wc, wctrans_t desc); Translates the wide character wc based on the mapping described by desc.
towlower4 wctype.h wint_t towlower (wint_t wc); Converts uppercase letter to lowercase letter.
towupper4 wctype.h wint_t towupper (wint_t wc); Converts lowercase letter to uppercase letter.
ungetc1 stdio.h int ungetc(int c, FILE *stream); Pushes c back onto the input stream.
ungetwc6
stdio.h
wchar.h
 wint_t ungetwc(wint_t wc, FILE *stream); Pushes the wide character wc back onto the input stream.
va_arg stdarg.h var_type va_arg(va_list arg_ptr, var_type); Returns the value of one argument and modifies arg_ptr to point to the next argument.
va_copy stdarg.h void va_copy(va_list dest, va_list src); Initializes dest as a copy of src.
va_end stdarg.h void va_end(va_list arg_ptr); Facilitates normal return from variable argument list processing.
va_start stdarg.h void va_start(va_list arg_ptr, variable_name); Initializes arg_ptr for subsequent use by va_arg and va_end.
vfprintf stdio.h stdarg.h int vfprintf(FILE *stream, const char *format, va_list arg_ptr); Formats and prints characters to the output stream using a variable number of arguments.
vfscanf stdio.h stdarg.h int vfscanf(FILE *stream, const char *format, va_list arg_ptr); Reads data from a specified stream into locations given by a variable number of arguments.
vfwprintf6
stdarg.h
stdio.h
wchar.h
 int vfwprintf(FILE *stream, const wchar_t *format, va_list arg); Equivalent to fwprintf, except that the variable argument list is replaced by arg.
vfwscanf stdio.h stdarg.h int vfwscanf(FILE *stream, const wchar_t *format, va_list arg_ptr); Reads wide data from a specified stream into locations given by a variable number of arguments.
vprintf stdio.h stdarg.h int vprintf(const char *format, va_list arg_ptr); Formats and prints characters to stdout using a variable number of arguments.
vscanf stdio.h stdarg.h int vscanf(const char *format, va_list arg_ptr); Reads data from stdin into locations given by a variable number of arguments.
vsprintf stdio.h stdarg.h int vsprintf(char *target-string, const char *format, va_list arg_ptr); Formats and stores characters in a buffer using a variable number of arguments.
vsnprintf stdio.h int vsnprintf(char *outbuf, size_t n, const char*, va_list); Same as vsprintf except that the function will stop after n characters have been written to outbuf.
vsscanf stdio.h stdarg.h int vsscanf(const char*buffer, const char *format, va_list arg_ptr); Reads data from a buffer into locations given by a variable number of arguments.
vswprintf
stdarg.h
wchar.h
 int vswprintf(wchar_t *wcsbuffer, size_t n, const wchar_t *format, va_list arg); Formats and stores a series of wide characters and values in the buffer wcsbuffer.
vswscanf stdio.h wchar.h int vswscanf(const wchar_t *buffer, const wchar_t *format, va_list arg_ptr); Reads wide data from a buffer into locations given by a variable number of arguments.
vwprintf6
stdarg.h
wchar.h
 int vwprintf(const wchar_t *format, va_list arg); Equivalent to wprintf, except that the variable argument list is replaced by arg.
vwscanf stdio.h wchar.h int vwscanf(const wchar_t *format, va_list arg_ptr); Reads wide data from stdin into locations given by a variable number of arguments.
wcrtomb4 wchar.h int wcrtomb (char *s, wchar_t wchar, mbstate_t *pss); Converts a wide character to a multibyte character. (Restartable version of wctomb.)
wcscat wchar.h wchar_t *wcscat(wchar_t *string1, const wchar_t *string2); Appends a copy of the string pointed to by string2 to the end of the string pointed to by string1.
wcschr wchar.h wchar_t *wcschr(const wchar_t *string, wchar_t character); Searches the wide-character string pointed to by string for the occurrence of character.
wcscmp wchar.h int wcscmp(const wchar_t *string1, const wchar_t *string2); Compares two wide-character strings, *string1 and *string2.
wcscoll4 wchar.h int wcscoll (const wchar_t *wcs1, const wchar_t *wcs2); Compares two wide-character strings using the collating sequence in the current locale.
wcscpy wchar.h wchar_t *wcscpy(wchar_t *string1, const wchar_t *string2); Copies the contents of *string2 (including the ending wchar_t null character) into *string1.
wcscspn wchar.h size_t wcscspn(const wchar_t *string1, const wchar_t *string2); Determines the number of wchar_t characters in the initial segment of the string pointed to by *string1 that do not appear in the string pointed to by *string2.
wcsftime wchar.h size_t wcsftime(wchar_t *wdest, size_t maxsize, const wchar_t *format, const struct tm *timeptr); Converts the time and date specification in the timeptr structure into a wide-character string.
wcslen wchar.h size_t wcslen(const wchar_t *string); Computes the number of wide-characters in the string pointed to by string.
wcslocaleconv locale.h struct wcslconv *wcslocaleconv(void); Formats numeric quantities in struct wcslconv according to the current locale.
wcsncat wchar.h wchar_t *wcsncat(wchar_t *string1, const wchar_t *string2, size_t count); Appends up to count wide characters from string2 to the end of string1, and appends a wchar_t null character to the result.
wcsncmp wchar.h int wcsncmp(const wchar_t *string1, const wchar_t *string2, size_t count); Compares up to count wide characters in string1 to string2.
wcsncpy wchar.h wchar_t *wcsncpy(wchar_t *string1, const wchar_t *string2, size_t count); Copies up to count wide characters from string2 to string1.
wcspbrk wchar.h wchar_t *wcspbrk(const wchar_t *string1, const wchar_t *string2); Locates the first occurrence in the string pointed to by string1 of any wide characters from the string pointed to by string2.
wcsptime wchar.h wchar_t *wcsptime ( const wchar_t *buf, const wchar_t *format, struct tm *tm ); Date and time conversion. Equivalent to strptime(), except that it uses wide characters.
wcsrchr wchar.h wchar_t *wcsrchr(const wchar_t *string, wchar_t character); Locates the last occurrence of character in the string pointed to by string.
wcsrtombs4 wchar.h size_t wcsrtombs (char *dst, const wchar_t **src, size_t len, mbstate_t *ps); Converts wide character string to multibyte string. (Restartable version of wcstombs.)
wcsspn wchar.h size_t wcsspn(const wchar_t *string1, const wchar_t *string2); Computes the number of wide characters in the initial segment of the string pointed to by string1, which consists entirely of wide characters from the string pointed to by string2.
wcsstr wchar.h wchar_t *wcsstr(const wchar_t *wcs1, const wchar_t *wcs2); Locates the first occurrence of wcs2 in wcs1.
wcstod wchar.h double wcstod(const wchar_t *nptr, wchar_t **endptr); Converts the initial portion of the wide-character string pointed to by nptr to a double value.
wcstod32 wchar.h _Decimal32 wcstod32(const wchar_t *nptr, wchar_t **endptr); Converts the initial portion of the wide-character string pointed to by nptr to a single-precision decimal floating-point value.
wcstod64 wchar.h _Decimal64 wcstod64(const wchar_t *nptr, wchar_t **endptr); Converts the initial portion of the wide-character string pointed to by nptr to a double-precision decimal floating-point value.
wcstod128 wchar.h _Decimal128 wcstod128(const wchar_t *nptr, wchar_t **endptr); Converts the initial portion of the wide-character string pointed to by nptr to a quad-precision decimal floating-point value.
wcstof wchar.h float wcstof(const wchar_t *nptr, wchar_t **endptr); Converts the initial portion of the wide-character string pointed to by nptr to a float value.
wcstok wchar.h wchar_t *wcstok(wchar_t *wcs1, const wchar_t *wcs2, wchar_t **ptr) Breaks wcs1 into a sequence of tokens, each of which is delimited by a wide character from the wide string pointed to by wcs2.
wcstol wchar.h long int wcstol(const wchar_t *nptr, wchar_t **endptr, int base); Converts the initial portion of the wide-character string pointed to by nptr to a long integer value.
wcstold wchar.h long double wcstold(const wchar_t *nptr, wchar_t **endptr); Converts the initial portion of the wide-character string pointed to by nptr to a long double value.
wcstombs stdlib.h size_t wcstombs(char *dest, const wchar_t *string, size_t count); Converts the wchar_t string into a multibyte string dest.
wcstoul wchar.h unsigned long int wcstoul(const wchar_t *nptr, wchar_t **endptr, int base); Converts the initial portion of the wide-character string pointed to by nptr to an unsigned long integer value.
wcsxfrm4 wchar.h size_t wcsxfrm (wchar_t *wcs1, const wchar_t *wcs2, size_t n); Transforms a wide-character string to values which represent character collating weights and places the resulting wide-character string into an array.
wctob
stdarg.h
wchar.h
 int wctob(wint_t wc); Determines whether wc corresponds to a member of the extended character set whose multibyte character representation is a single byte when in the initial shift state.
wctomb stdlib.h int wctomb(char *string, wchar_t character); Converts the wchar_t value of character into a multibyte string.
wctrans wctype.h wctrans_t wctrans(const char *property); Constructs a value with type wctrans_t that describes a mapping between wide characters identified by the string argument property.
wctype4 wchar.h wctype_t wctype (const char *property); Obtains handle for character property classification.
wcwidth wchar.h int wcswidth(const wchar_t *pwcs, size_t n); Determine the display width of a wide character string.
wmemchr wchar.h wchar_t *wmemchr(const wchar_t *s, wchar_t c, size_t n); Locates the first occurrence of c in the initial n wide characters of the object pointed to by s.
wmemcmp wchar.h int wmemcmp(const wchar_t *s1, const wchar_t *s2, size_t n); Compares the first n wide characters of the object pointed to by s1 to the first n characters of the object pointed to by s2.
wmemcpy wchar.h wchar_t *wmemcpy(wchar_t *s1, const wchar_t *s2, size_t n); Copies n wide characters from the object pointed to by s2 to the object pointed to by s1.
wmemmove wchar.h wchar_t *wmemmove(wchar_t *s1, const wchar_t *s2, size_t n); Copies n wide characters from the object pointed to by s2 to the object pointed to by s1.
wmemset wchar.h wchar_t *wmemset(wchar_t *s, wchar_t c, size_t n); Copies the value of c into each of the first n wide characters of the object pointed to by s.
wprintf6 wchar.h int wprintf(const wchar_t *format, arg-list); Equivalent to fwprintf with the argument stdout interposed before the arguments to wprintf.
wscanf6 wchar.h int wscanf(const wchar_t *format, arg-list); Equivalent to fwscanf with the argument stdin interposed before the arguments of wscanf.
y0 math.h double y0(double x); Calculates the Bessel function value of the second kind of order 0.
y1 math.h double y1(double x); Calculates the Bessel function value of the second kind of order 1.
yn math.h double yn(int n, double x); Calculates the Bessel function value of the second kind of order n.
Note: 1 This function is not supported for files opened with type=record.
Note: 2 This function is not supported for files opened with type=record and mode=ab+, rb+, or wb+.
Note: 3 The ILE C compiler only supports fully buffered and line-buffered streams. Since a block and a line are equal to the record length of the opened file, fully buffered and line-buffered streams are supported in the same way. The setbuf() and setvbuf() functions have no effect.
Note: 4 This function is not available when LOCALETYPE(*CLD) is specified on the compilation command.
Note: 5 This function is available only when SYSIFCOPT(*IFSIO) is specified on the CRTCMOD or CRTBNDC command.
Note: 6 This function is not available when either LOCALETYPE(*CLD) or SYSIFCOPT(*NOIFSIO) is specified on the compilation command.