Advanced Programming: ANSI C Library

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2.14 ANSI C Library

Listed below are the most important of the ANSI C standard library functions.

The header file where related definitions are stored are given (these may vary on some systems so check local reference manuals).

A brief description is included with all parameter types. More info can be obtained from online help or reference manuals.

2.14.1 Buffer Manipulation

#include <memory.h>

`void memchr (void s, int c, size_t n)`	`Search for a character in a buffer`
`int memcmp (void s1, void s2, size_t n)`	`Compare two buffers`
`void memcpy (void dest, void *src, size_t n)`	`Copy one buffer into another`
`void memmove (void dest, void *src, size_t n)`	`Move a number of bytes from one buffer to another`
`void memset (void s, int c, size_t n)`	`Set all bytes of a buffer to a given character`

2.14.2 Character Classification and Conversion

#include <ctype.h>

`int isalnum(int c)`	`True if c is alphanumeric.`
`int isalpha(int c)`	`True if c is a letter.`
`int isascii(int c)`	`True if c is ASCII.`
`int iscntrl(int c)`	`True if c is a control character.`
`int isdigit(int c)`	`True if c is a decimal digit.`
`int isgraph(int c)`	`True if c is a graphical character.`
`int islower(int c)`	`True if c is a lowercase letter.`
`int isprint(int c)`	`True if c is a printable character.`
`int ispunct (int c)`	`True if c is a punctuation character.`
`int isspace(int c)`	`True if c is a space character.`
`int isupper(int c)`	`True if c is an uppercase letter.`
`int isxdigit(int c)`	`True if c is a hexadecimal digit.`
`int toascii(int c)`	`Convert c to ASCII.`
`int tolower(int c)`	`Convert c to lowercase.`
`int toupper(int c)`	`Convert c to uppercase.`

2.14.3 Data Conversion

#include <stdlib.h>

`double atof(char *string)`	`Convert string to floating point value.`
`int atoi(char *string)`	`Convert string to an integer value.`
`int atol(char *string)`	`Convert string to a long integer value.`
`char itoa(int value, char string, int radix)`	`Convert an integer value to a string using given radix.`
`char ltoa(long value, char string, int radix)`	`Convert long integer to string in a given radix.`
`double strtod(char string, char endptr)`	`Convert string to a floating point value.`
`long strtol(char string, char endptr, int radix)`	`Convert string to a long integer using a given radix.`
`unsigned long strtoul(char string, char endptr, int radix)`	`Convert string to unsigned long.`

2.14.4 Directory Manipulation

#include <dir.h>

`int chdir(char *path)`	`Change current directory to given path.`
`char getcwd(char path, int numchars)`	`Returns name of current working directory.`
`int mkdir(char *path)`	`Create a directory u sing given path name.`
`int rmdir(char *path)`	`Delete a specified directory.`

2.14.5 File Manipulation

#include <sys/stat.h>
#include <sys/types.h>

`int chmod(char *path, int pmode)`	`Change permission settings of a file.`
`int fstat(int handle, struct stat *buffer)`	`Get file status information.`
`int remove(char *path)`	`Delete a named file.`
`int rename(char oldname, char newname)`	`rename a file.`
`int stat(char path, struct stat buffer)`	`Get file status information of named file.`
`unsigned umask(unsigned pmode)`	`Set file permission mask.`

2.14.6 Input and Output (Stream I/O)

#include <stdio.h>

`void clearerr(FlLE *file_pointer)`	`Clear error indicator of stream,`
`int fclose(FlLE *file_pointer)`	`Close a file,`
`int feof(FlLE *file_pointer)`	`Check if end of file occurred on a stream.`
`int ferror(FlLE *file_pointer)`	`Check if any error occurred during file I/0.`
`int fflush(FlLE *file_pointer)`	`Write out (flush) buffer to file.`
`int fgetc(FlLE *file_pointer)`	`Get a character from a stream.`
`int fgetpos(FlLE *file_pointer, fpos_t current_pos)`	`Get the current position in a stream.`
`char fgets(char string, int maxchar, FILE *file_pointer)`	`Read a string from a file.`
`FILE fopen(char filename, char *access_mode)`	`Open a file for buffered I/0.`
`int fprintf(FlLE file_pointer, char format_string, args)`	`Write formatted output to a file,`
`int fputc(int c, FILE *file_pointer)`	`Write a character to a stream.`
`int fputchar(int c)`	`Write a character to stdout.`
`int fputs(char string, FILE file_pointer)`	`Write a string to a stream.`
`size_t fread(char buffer, size_t size size_t count, FILE file_pointer)`	`Read unformatted data from a stream into a buffer.`
`FILE freopen(char filename, char access mode, FILE file_pointer)`	`Reassign a file pointer to a different file.`
`int fscanf(FlLE file_pointer, char format string, args)`	`Read formatted input from a stream.`
`int fseek(FlLE *file_pointer, long offset, int origin)`	`Set current position in file to a new location.`
`int fsetpos(FlLE file pointer, fpos_t current pos)`	`Set current position in file to a new location.`
`long ftell(FlLE *file_pointer)`	`Get current location in file.`
`size_t fwrite(char buffer, size_t size, size_t count FILE file_pointer)`	`Write unformatted data from a buffer to a stream.`
`int getc(FlLE *file_pointer)`	`Read a character from a stream.`
`int getchar(void)`	`Read a character from stdin.`
`char gets(char buffer)`	`Read a line from stdin into a buffer.`
`int printf(char *format _string, args)`	`Write formatted output to stdout.`
`int putc(int c, FILE *file_pointer)`	`Write a character to a stream.`
`int putchar(int c)`	`Write a character to stdout.`
`int puts(char *string)`	`Write a string to stdout.`
`void rewind(FlLE *file_pointer)`	`Rewind a file.`
`int scanf(char *format_string, args)`	`Read formatted input from stdin.`
`void setbuf(FlLE file_pointer, char buffer)`	`Set up a new buffer for the stream.`
`int setvbuf(FlLE file_pointer, char buffer, int buf_type, size_t buf size)`	`Set up new buffer and control the level of buffering on a stream.`
`int sprintf(char string, char format_string, args)`	`Write formatted output to a string.`
`int sscanf(char buffer, char format_string, args)`	`Read formatted input from a string.`
`FILE *tmpfile(void)`	`Open a temporary file.`
`char tmpnam(char file_name)`	`Get temporary file name.`
`int ungetc(int c, FILE *file_pointer)`	`Push back character into stream' s buffer`

2.14.7 Mathematics

#include <math.h>

`int abs (int n)`	`Get absolute value of an integer.`
`double acos(double x)`	`Compute arc cosine of x.`
`double asin(double x)`	`Compute arc sine of x.`
`double atan(double x)`	`Compute arc tangent of x.`
`double atan2(double y, double x)`	`Compute arc tangent of y/x.`
`double ceil(double x)`	`Get smallest integral value that exceeds x.`
`double cos(double x)`	`Compute cosine of angle in radians.`
`double cosh(double x)`	`Compute the hyperbolic cosine of x.`
`div_t div(int number, int denom)`	`Divide one integer by another.`
`double exp(double x`	`Compute exponential of x.`
`double fabs (double x )`	`Compute absolute value of x.`
`double floor(double x)`	`Get largest integral value less than x.`
`double fmod(double x, double y)`	`Divide x by y with integral quotient and return remainder.`
`double frexp(double x, int *expptr)`	`Breaks down x into mantissa and exponent of no.`
`long labs(long n)`	`Find absolute v alue of long integer n.`
`double ldexp(double x, int exp)`	`Reconstructs x out of mantissa and exponent of two.`
`ldiv_t ldiv(long number, long denom)`	`Divide one long integer by another.`
`double log(double x)`	`Compute log(x).`
`double log10 (double x )`	`Compute log to the base 10 of x.`
`double modf(double x, double *intptr)`	`Breaks x into fractional and integer parts.`
`double pow (double x, double y)`	`Compute x raised to the power y.`
`int rand (void)`	`Get a random integer between 0 and 32.`
`int random(int max_num)`	`Get a random integer between 0 and max_num.`
`void randomize(void)`	`Set a random seed for the random number generator.`
`double sin(double x)`	`Compute sine of angle in radians.`
`double sinh(double x)`	`Compute the hyperbolic sine of x.`
`double sqrt(double x)`	`Compute the square root of x.`
`void srand(unsigned seed)`	`Set a new seed for the random number generator (rand).`
`double tan(double x)`	`Compute tangent of angle in radians.`
`double tanh(double x)`	`Compute the hyperbolic tangent of x.`

2.14.8 Memory Allocation

#include <malloc.h>

`void *calloc(size_t num elems, size_t elem_size)`	`Allocate an array and initialize all elements to zero.`
`void free(void *mem address)`	`Free a block of memory.`
`void *malloc(size_t num bytes)`	`Allocate a block of memory.`
`void realloc(void mem address, size_t news i ze)`	`Reallocate (adjust size) a block of memory.`

2.14.9 Process Control

#include <stdlib.h>

`void abort(void)`	`Abort a process.`
`int execl(char path, char argO, char *arg1,..., NULL)`	`Launch a child process (pass command line).`
`int execlp(char path, char argO, char *arg1,..., NULL)`	`Launch child (use PATH pass command line).`
`int execv(char path, char argv[])`	`Launch child (pass argument vector).`
`int execvp(char path, char argv[])`	`Launch child (use PATH, pass argument vector).`
`void exit(int status)`	`Terminate process after flushing all buffers.`
`char getenv(char varname)`	`Get definition of environment variable,`
`void perror(char *string)`	`Print error message corresponding to last system error.`
`int putenv(char *envstring)`	`Insert new definition into environment table.`
`int raise(int signum)`	`Generate a C signal (exception).`
`void (signal(int signum, void(func)(jnt signum [, int subcode])))(int signum)`	`Establish a signal handler for signal number signum.`
`int system(char *string)`	`Execute an operating system command.`

2.14.10 Searching and Sorting

#include <stdlib.h>

`void bsearch(void key, void base, size_t num, size_t width, int (compare)(void elem1, void elem2))`	`Perform binary search.`
`void qsort(void base, size_t num, size_t width, int (compare)(void elem1, void elem2))`	`Use the quicksort algorithm to sort an array.`

2.14.11 String Manipulation

#include <string.h>

`char stpcpy (char dest, char *src)`	`Copy one string into another.`
`int strcmp(char string1, char string2)`	`Compare string1 and string2 to determine alphabetic order.`
`char strcpy(char string1, char *string2)`	`Copy string2 to stringl.`
`char *strerror(int errnum)`	`Get error message corresponding to specified error number.`
`int strlen(char *string)`	`Determine the length of a string.`
`char strncat(char string1, char *string2, size_t n)`	`Append n characters from string2 to stringl.`
`int strncmp(char string1, char string2, size_t n)`	`Compare first n characters of two strings.`
`char strncpy(char string1, char *string2, size_t n)`	`Copy first n characters of string2 to stringl.`
`char strnset(char string, int c, size _t n)`	`Set first n characters of string to c.`
`char strrchr(char string, int c)`	`Find last occurrence of character c in string.`

2.14.12 Time

#include <time.h>

`char asctime (struct tm time)`	`Convert time from struct tm to string.`
`clock_t clock(void)`	`Get elapsed processor time in clock ticks.`
`char ctime(time_t time)`	`Convert binary time to string.`
`double difftime(time_t time2, time_t time1)`	`Compute the difference between two times in seconds.`
`struct tm gmtime (time_t time)`	`Get Greenwich Mean Time (GMT) in a tm structure.`
`struct tm localtime(time_t time)`	`Get the local time in a tm structure.`
`time_t time(time_t *timeptr)`	`Get current times as seconds elapsed since 0 hours GMT 1/1/70.`