Program modify text file

Record a search as part of a macro to instantly edit all search matches in any particular way. Save any number of macros to build your own library of high-octane text editing wizards. Use rectangular selections to easily edit columns of text. Any editing command that works on a usual linear selection also works on a rectangular selection. Shift and insert columns left and right, move blocks up and down, fill and indent blocks, etc. Handy commands to begin, end, shrink and expand selections make it easy to work with blocks spanning many pages.

Easily edit all kinds of lists with handy commands to sort lines alphabetically and delete duplicate lines. Use these commands with rectangular selections to sort and trim lists of multiple columns on one of the columns.

Of course, you can always turn this option off. Get statistics for just the current file, or for all files in a project, or even all files in all projects. Easily insert special symbols like the trademark or copyright symbol into your documents, or enter letters from a foreign script that your keyboard does not support. To handle reading the file into a buffer, the link posted overwriting a specific line on a text file? Your case is different.

Specifically the use of fseek and ftell. Using fseek and ftell provides a simply way to determine the size or length of the file that can then be used to allocate space to hold the entire file in memory.

Below is one approach to a simple function that takes the address of a character pointer and a file pointer, then using fseek and ftell allocates the required memory to hold the file and then reads the file into the buffer filebuf in a single operation with fread. The buffer is filled, in place, and also returned. A pointer to the file length fplen is passed to the function so the length is made available back in the calling function main in this case.

Once you have the file in memory, the second piece of the puzzle is simply to scan through the buffer and make the replacements you need. The function returns the number of replacements made so you can determine whether a write out to the original filename is required:. Putting all the pieces together in a short example program using your sample data could be written as follows.

The program expects the filename as the first argument or it will read from stdin and write to stdout by default if no filename is given. There are always additional validation checks you can include as well:.

In any code your write that dynamically allocates memory, you have 2 responsibilites regarding any block of memory allocated: 1 always preserves a pointer to the starting address for the block of memory so, 2 it can be freed when it is no longer needed. For Linux valgrind is the normal choice. There are many subtle ways to misuse a new block of memory. Using a memory error checker allows you to identify any problems and validate proper use of of the memory you allocate rather than finding out a problem exist through a segfault.

There are similar memory checkers for every platform. They are all simple to use, just run your program through it. Look over the code and understand what it is doing. Let me know if you have questions. Actually, txt file is just a sequence of bytes. So, if you rewrite some line, you have to move data lines remained in the file just after your new line. But if your new line has the same length as before, you can write it over old line without any worries. Then you go line by line in the read file until you find a line that you wish to change, then you rewrite the line yourself in the new copy file.

Then skip that line in the read file and continue on. After the copy file is what you want, you can replace the name of it to the original file name you want it to have. Then it will act as if you edited the file like you wanted to. Stack Overflow for Teams — Collaborate and share knowledge with a private group. Create a free Team What is Teams? Collectives on Stack Overflow. Learn more.

How to edit a specific line of a txt file in C Ask Question. Replacing Text could be either erasing the entire content of the file and replacing it with new text or it could mean modifying only specific words or sentences within the existing text. Method 1 : Removing all text and write new text in the same file In this method we replacing all the text stored in the text file, for this, we will open the file in reading and writing mode and it will rewrite all the text.

Then, the desired line can be replaced by using the replace function. Finally, the file is opened in the write mode, and the replaced content is written in the given file. Skip to content. Change Language. Related Articles. Table of Contents. Improve Article. Save Article. Like Article.