Input and Output Routines: < stdio.h>

File open and close:

fopen
opens a file stream
freopen
open a file and associate with a stream
fflush
flushes an output file stream buffer
fclose
closes a file stream

File management:

remove
removes a named file
rename
renames an old file name to a new name
tmpfile
creates a temporary file
setbuf
sets a file stream as buffered or unbuffered

Formatted I/O:

fprintf
writes to a file
printf
writes to standard output
sprintf
writes to a string

fscanf
reads from a file
scanf
reads from standard input
sscanf
reads from a string

Character and String I/O:

fgetc
reads a character from a file
fgets
reads a string from a file
fputc
writes a character to a file
fputs
writes a string to a file
getc
reads a character from a file
getchar
reads a character from standard input
gets
reads a string from standard input
putc
writes a character to a file
putchar
writes a character to standard output
puts
writes a string to standard output
ungetc
puts a character back onto a stream; only one character per stream may be allowed to be put back

Block I/O:

fread
reads a block from a file
fwrite
writes a block to a file

File Pointer Positioning:

fseek
seeks a position in a file stream
ftell
returns a position in a stream
rewind
essentially reopens a file
fgetpos
gets current position in a stream
fsetpos
sets the current position in a stream

File Error Handling:

clearerr
clears error and end of file indicators
feof
chaecks end of file indicator
ferror
checks file error indicator
perror
prints a specified string and an error message for errno