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) Ring programming language