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(exefolder() + "../tests/scripts/s65.ring","r")
See "reopen" + nl
fp = freopen(exefolder() + "../tests/scripts/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(exefolder() + "../tests/scripts/mytest2.txt")
write(exefolder() + "../tests/scripts/tests1.txt","hello")
rename(exefolder() + "../tests/scripts/test1.txt",exefolder() +
"../tests/scripts/mytests2.txt")
see "print file" + nl
fp = fopen(exefolder() + "../samples/fromdoc/filefuncs.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(exefolder() + "../samples/fromdoc/filefuncs.ring","r")
r = fgets(fp,33)
see r + nl
fclose(fp)
fp = fopen(exefolder() + "../tests/scripts/test78.txt","w+")
fseek(fp,0,2) # goto end of file
fputc(fp,"t")
fputc(fp,"e")
fputc(fp,"s")
fputc(fp,"t")
fputs(fp,"tests2")
fclose(fp)
see "print file" + nl
see read(exefolder() + "../tests/scripts/test78.txt")
fp = fopen(exefolder() + "../tests/scripts/test78.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(exefilename(),"rb")
r = fread(fp,100)
see r + nl
fclose(fp)
see "testing fwrite() " + nl
fp = fopen(exefolder() + "../tests/scripts/test1.txt","wb")
fwrite(fp,r)
fclose(fp)
The next example print part of the content of a binary file
see "Testing: fread()" +" FileName: "+ exefilename() +nl +nl
fp = fopen(exefilename(),"rb")
r = fread(fp,800)
for n =1 to len(r)
if isprint(substr(r, n, 1))
see substr(r, n, 1)
else
see "."
ok
### 80 char per line
if n % 80 = 0
see nl
ok
next
fclose(fp)