Ring/Lessons/Files

Files

In this chapter we are going to learn about files functions.

Read()
Write()
Dir()
Rename()
Remove()
fopen()
fclose()
fflush()
freopen()
tempfile()
tempname()
fseek()
ftell()
rewind()
fgetpos()
fsetpos()
clearerr()
feof()
ferror()
perror()
fgetc()
fgets()
fputc()
fputs()
ungetc()
fread()
fwrite()
fexists()

Read() Function

We can read the file content using the Read() function

Syntax:

	Read(cFileName) ---> String contains the file content

Example:

	see read("myfile.txt")

The read function can read binary files too

Example:

	see read("myapp.exe")

Write() Function

We can write string to file using the Write() function

The write function can write binary data to binary files.

Syntax:

	Write(cFileName,cString)	# write string cString to file cFileName

Example:

	# copy file
	cFile = read("ring.exe")
	write("ring2.exe",cFile)

Dir() Function

We can get the folder contents (files & sub folders) using the Dir() function.

Syntax:

	Dir(cFolderPath) ---> List contains files & sub folders.

This function returns a list and each list item is a list of two items

File/sub folder name

Type (0 = File , 1 = Folder/Directory)

Example:

	see "Testing DIR() " + nl
	mylist = dir("C:\myfolder")
	for x in mylist
		if x[2] 
			see "Directory : " + x[1] + nl
		else
			see "File : " + x[1] + nl
		ok
	next
	see "Files count : " + len(mylist)

Rename() Function

We can rename files using the Rename() function

Syntax:

	Rename(cOldFileName,cNewFileName)

Example:

	rename("file.txt","help.txt")

Remove() Function

We can delete a file using the Remove() function

Syntax:

	Remove(cFileName)

Example:

	remove("test.txt")

Fopen() Function

We can open a file using the Fopen() function

Syntax:

	Fopen(cFileName,cMode) ---> File Handle

=====	==========================================
Mode	Description
=====	==========================================
"r"     Reading (The file must exist)
"w"     Writing (create empty file / overwrite)
"a"     Appends (create file if it doesn't exist)
"r+"    update (reading/writing)
"w+"    Create empty file (reading/writing)
"a+"    reading & appending
=====	==========================================

Fclose() Function

When we open a file using fopen() function, we can close it using the Fclose() function

Syntax:

	Fclose(file handle)

Fflush() Function

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

Syntax:

	Fflush(file handle)

Freopen() Function

We can open another file using the same file handle and at the same file close the old file

Syntax:

	Freopen(cFileName,cMode,file handle) ---> file handle

Example:

	freopen("myprogoutput.txt","w+",stdout)
	see "welcome" + nl
	for x = 1 to 10
		see x + nl
	next

/* ** Read : https://en.wikipedia.org/wiki/Device_file#Device_files ** The next code is not portable, we can use iswindows() before ** using it and we can write special code for each operating system. */

freopen("CON","w",stdout) # For Microsoft Windows see "Done" + nl # print to stdout again

Output:

	# Output to stdout
	Done

# Output to file : myprogoutput.txt welcome 1 2 3 4 5 6 7 8 9 10

Tempfile() Function

The function Tempfile() creates a temp. file (binary).

The file will be deleted automatically when the stream is closed

Syntax:

	TempFile() ---> file handle

Tempname() Function

We can generate temp. file name using the Tempname() function

The generated name will be different from the name of any existing file

Syntax:

	Tempname() ---> generated file name as string

Fseek() Function

We can set the file position of the stream using the Fseek() function

Syntax:

	Fseek(file handle, nOffset, nWhence) ---> zero if successful

The next table presents the nWhence values

=====	===============================
Value	Description
=====	===============================
0       Beginning of file
1       Current position
2       End of file
=====	===============================

Ftell() Function

We can know the current file position of a stream using the Ftell() function

Syntax:

	Ftell(file handle) ---> file position as number

Rewind() Function

We can set the file position to the beginning of the file using the Rewind() function

Syntax:

	
	Rewind(file handle)

Fgetpos() Function

We can get handle to the current file position using the Fgetpos() function

Syntax:

	Fgetpos(file handle) ---> position handle

Fsetpos() Function

We can set the current file position using the Fgetpos() function

Syntax:

	Fsetpos(file handle,position handle)

Clearerr() Function

We can clear the EOF error and the error indicators of a stream using the clearerr() function

Syntax:

	Clearerr(file handle)

Feof() Function

We can test the end-of-file indicator using the Feof() function

Syntax:

	Feof(file handle) ---> returns 1 if EOF and 0 if not

Ferror() Function

We can test the error indicator of a given stream using the Ferror() function

Syntax:

	Ferror(file handle) ---> returns 1 if error and 0 if not

Perror() Function

We can print error message to the stderr using the Perror() function

Syntax:

	Perror(cErrorMessage)

Fgetc() Function

We can get the next character from the stream using the Fgetc() function

Syntax:

	Fgetc(file handle) ---> returns character or EOF

Fgets() Function

We can read new line from the stream using the Fgets() function

Syntax:

	Fgets(file handle,nSize) ---> string

The function stop when nSize characters are read, new line character is read or EOF.

Fputc() Function

We can write a character to the stream using the Fputc() function

Syntax:

	Fputc(file handle,cChar)

Fputs() Function

We can write a string to the stream using the Fputs() function

Syntax:

	Fputs(file handle,cString)

Ungetc() Function

We can push a character to the stream using the Ungetc() function

The character will be available for the next read

Syntax:

	Ungetc(file handle,character)

Fread() Function

We can read data from a stream using the Fread() function

Syntax:

	Fread(file handle,nSize)

Fwrite() Function

We can write data to a stream using the Fwrite() function

Syntax:

	Fwrite(file handle,cString)

Fexists() Function

We can check if a file exists using the Fexists() function

Syntax:

	Fexists(cFileName) ---> returns 1 if the file exists

Example:

	see fexists("b:\mahmoud\apps\ring\ring.exe") + nl +
	    fexists("b:\mahmoud\apps\ring\ring2.exe") + nl

Output:

	1
	0

Example

The next program test some of the file functions

	See "Testing file functions" + nl

	See "open file" + nl
	fp = fopen("tests\s65.ring","r")

	See "reopen" + nl
	fp = freopen("tests\s78.ring","r",fp)
	See "close file" + nl
	fclose(fp)

	see "temp file" + nl
	fp = tempfile()
	fclose(fp)

	see "temp name" + nl
	see tempname() + nl

	remove("tests\mytest1.txt")
	write("tests\test1.txt","hello")
	rename("tests\test1.txt","tests\mytest2.txt")

	see "print file" + nl
	fp = fopen("tests\file.ring","r")
	r = fgetc(fp)
	while isstring(r)
		see r
		r = fgetc(fp)
	end
	fclose(fp)

	see nl+"print line from the file" + nl
	fp = fopen("tests\file.ring","r")
	r = fgets(fp,100)
	see r
	fclose(fp)

	fp = fopen("tests\myfile.txt","rw+")
	fseek(fp,0,2) # goto end of file
	fputc(fp,"t")
	fputc(fp,"e")
	fputc(fp,"s")
	fputc(fp,"t")
	fputs(fp,"test2")
	fclose(fp)

	see "print file" + nl
	see read("tests\myfile.txt")

	fp = fopen("tests\myfile.txt","r")
	see "testing ungetc() " + nl
	for x = 1 to 3
		r = fgetc(fp)
		see r + nl
		ungetc(fp,r)
	next
	fclose(fp)

	see "testing fread() " + nl
	fp = fopen("ring.exe","r")
	r = fread(fp,100)
	see r + nl
	fclose(fp)

	see "testing fwrite() " + nl
	fp = fopen("tests\myfile.txt","wb")
	fwrite(fp,r)
	fclose(fp)

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