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()
Numbers and Bytes
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) ---> Number ( Status: Success (0) , Error (-1) )
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 time 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 Fsetpos() 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)
Numbers and Bytes¶
The next functions to convert between Numbers and Bytes.
Int2Bytes()
Float2Bytes()
Double2Bytes()
Bytes2Int()
Bytes2Float()
Bytes2Double()
Example:
see "Test Int2Bytes() and Bytes2Int() - Value : 77" + nl
r = Int2Bytes(77)
see "Int Size : " + len(r) + nl
see r + nl
see Bytes2Int(r) + nl
see "Test Float2Bytes() and Bytes2Float() - Value 77.12" + nl
r = Float2Bytes(77.12)
see "Float Size : " + len(r) + nl
see r + nl
see Bytes2Float(r) + nl
see "Test Double2Bytes() and Bytes2Double() - Value 9999977.12345" + nl
r = Double2Bytes(9999977.12345)
see "Double Size : " + len(r) + nl
see r + nl
decimals(5)
see Bytes2Double(r) + nl