C Programming

int fseek(FILE *stream, long offset, int origin)
fseek sets the file position for stream; a subsequent read or write will access data beginning at the new position. For a binary file, the position is set to offset characters from origin, which may be SEEK_SET (beginning), SEEK_CUR (current position), or SEEK_END (end of file). For a text stream, offset must be zero, or a value returned by ftell (in which case origin must be SEEK_SET). fseek returns non-zero on error. (more…)

Many of the functions in the library set status indicators when error or end of file occur. These indicators may be set and tested explicitly. In addition, the integer expression errno (declared in <errno.h>) may contain an error number that gives further information about the most recent error.
void clearerr(FILE *stream) (more…)

The header <ctype.h> declares functions for testing characters. For each function, the argument list is an int, whose value must be EOF or representable as an unsigned char, and the return value is an int. The functions return non-zero (true) if the argument c satisfies the condition described, and zero if not.
isalnum(c) isalpha(c) or isdigit(c) is true (more…)

There are two groups of string functions defined in the header <string.h>. The first have names beginning with str; the second have names beginning with mem. Except for memmove, the behavior is undefined if copying takes place between overlapping objects. Comparison functions treat arguments as unsigned char arrays.
In the following table, variables s and t are of type char *; cs and ct are of type const char *; n is of type size_t; and c is an int converted to char (more…)