Question

I have big sql file, i need to change some lines there, now i have such data in my file

 INSERT INTO `LINK_LA_TYP` VALUES
 ('1','8917181','1','24','2'),
 ('1','8934610','1','24','1'),
 ('1','9403766','1','30','1'),
 ('1','9422299','1','30','2'),

I done that, for example on $count line i write one more

INSERT INTO LINK_LA_TYP VALUES

but then my file looks like this:

INSERT INTO `LINK_LA_TYP` VALUES
 ('1','8917181','1','24','2'),
 ('1','8934610','1','24','1'),
 ('1','9403766','1','30','1'),
 INSERT INTO `LINK_LA_TYP` VALUES
 ('1','9422299','1','30','2'),

But i need that previous line symbol , change to ; How i can do this in big file?
So i need to see file and write there line(done) and then change , to ; on previous line, and do this on every ~500 line (depends on counter) to the end of file

Answer 1

This is the simplest workflow:

Create a temporary file. Then:

• Read one line at a time from the original file
• Do your work on that line
• Write the changed line to the temporary file
• Repeat.

When you are done, simply rename the temp file to the correct filename, which will remove the old file.

---

If each line are going to be the exact same size as before, you may instead change the file inline. You can do this by aligning the file pointer correctly with fseek and then writing. This is a little bit trickier to achieve but may save you the space for the temp file (and possibly be a little bit faster as well). This is only possible if the resulting file size will be exactly the same as the original file size (e.g., if you only change certain bytes from one character to another).