Useful Functions

Several useful functions you will want to be aware of from the c library include:

• size_t strlen (const char *s) calculates the size of null-terminated strings.

• int strcmp (const char *sl, const char *s2) compares two strings alphabetically.

• char * strdup (const char *s) takes the pointer to a string, and creates a new copy in a new location, and returns the new location.

• FILE * fopen (const char *filename, const char *opentype) opens a managed, buffered file (allows easier reading and writing than using file descriptors directly).^[3], ^[4]

• int fclose (FILE * stream) closes a file opened with fopen.

• char * fgets (char *s, int count, FILE *stream) fetches a line of characters into string s.

• int fputs (const char *s, FILE *stream) writes a string to the given open file.

• int fprintf (FILE *stream, const char *template, ...) is just like printf, but it uses an open file rather than defaulting to using standard output.

You can find the complete manual on this library by going to http://www.gnu.org/software/libc/manual/

^[3]stdin, stdout, and stderr (all lower case) can be used in these programs to refer to the files of their corresponding file descriptors.

^[4]FILE is a struct. You don't need to know its contents to use it. You only have to store the pointer and pass it to the relevant other functions.