Ring Documentation Walkthrough #12.1 – Advanced Read & Write Files

Hello, We’ll go through some advanced operations about the files.

File Handling:

We will learn in the next example these functions:

  • fopen – open a file
  • fgets – read a specific amount of a file
  • fgetc – read a character of a file
  • fexists – check if a file exists
  • freopen – re-open a file in a file handler
  • fseek ( file_handle, offset, whence – set the position of the stream, whence: ( 0=beginning of the file, 1=current position, 2=end of the file)
  • rewind – set back the position to the beginning of the file
  • fgetpos & fsetpos – get handle of the current position and set new position for the file
  • fputc – write a single character
  • fputs – write a text
  • fwrite – write a text
  • fread – read a specific amount of a file
  • ftell – know the current position
  • fclose – close the file handler

/*
r - read
w - write new or overwrite
a - appends and creates new if doesn't exists
r+ - read & write (update file)
w+ - read & write
a+ - read & append
*/
file = fopen('somewhere.txt', 'r')
see file[1]
see fgets(file, 100) #the same result as above.

see fgetc(file) #returns a character or EOF

see fexists('some_other_file.txt') #returns 0 (false), 1 (true)

file = freopen('some_other_file.txt', 'r+')
fseek(file, 0 , 2) #go to the end of the text file
see ftell(file)
fputc(file, 'a') #append a character
fputs(file, 'amr') #append a text

rewind(file) #set back the position to the beginning of the file.

fwrite(file, 'consider this a something just for the example, ty.') #writes to the file

fread(file, 100) #returns 100 characters from the file

x = fgetpos(file) #returns position handle
fsetpos(file, 5) #set new position of the file
fclose(file) #close the file handler.

Temperory files:

There’re two functions for this.

x = tempfile() #returns a file handle for a temp file.
x = tempname() #returns a temp file name that doesn't exists

Errors:

  • clearerr

    clearerr(file) #clear the EOF error and the error indicators of a stream.
    
  • feof

    see feof(file) #returns 1 if it's the end of the file, 0 if it's not.
    
  • ferror

    see ferror(file) #returns 1 if there's error indicator, 0 if not.
    
  • perror

    perror('error happened') #print error message to the stderr.
    

fflush:

We can flushes the output buffer of a stream using the Fflush() function.

fflush(file)

ungetc:

We can push a character to the stream using this function so
the character will be available for the next read.

ungetc(file, 'a')

Well, at this point we’re done of the files chapter.

see you in the next chapter.

amrESSAM.

Advertisements
Ring Documentation Walkthrough #12.1 – Advanced Read & Write Files

Leave a Reply

Fill in your details below or click an icon to log in:

WordPress.com Logo

You are commenting using your WordPress.com account. Log Out / Change )

Twitter picture

You are commenting using your Twitter account. Log Out / Change )

Facebook photo

You are commenting using your Facebook account. Log Out / Change )

Google+ photo

You are commenting using your Google+ account. Log Out / Change )

Connecting to %s