run-count – Counting program runs – Computer Science by Example

run-count – Counting program runs

Write a program that prints how many times it has been run by means of a runcount.txt file like so:

$ ./run-count
run #1
$ ./run-count
run #2
$ ./run-count
run #3

If it is the first time your program is running in the working directory, a runcount.txt file should be created with the number 1 and your program should print run #1. Each time your program is run, the number n in the runcount.txt file should be incremented and your program should print run #n.

Run count

The number should be stored in the file in a proper line, i.e., followed by a line break.

Scoring

12/12: works

Hints

To avoid issues with seeking the correct position on the runcount.txt file, you can open and close the file twice: first for getting the current run count; then for writing the updated run count. This way you will not have to worry about positioning the reading or writing pointers on the file as whenever you reopen a file the pointer is positioned at the beginning.

Do not forget to follow the number in runcount.txt by a line break.

Your program should return 0 regardless of where the runcount.txt file is found or not in the first run. If your program yields an error code of 1, it indicates to the system that there was an error with runtime and it will be marked as such. (runtime error)

This is what should happen when you run your program on an “empty” folder without an initial runcount.txt file:
```
 $ ls
 run-count.c
```
You compile the code:
```
 $ gcc run-count.c -o run-count
```
An executable appears in the working directory:
```
 $ ls
 run-count  run-count.c
```
You run the program the first time, it prints run #1 with a proper line break:
```
 $ ./run-count
 run #1
```
A runcount.txt file appears in the working directory:
```
 $ ls
 run-count  run-count.c  runcount.txt
```
That file should have 1 followed by a line break after the first run:
```
 $ cat runcount.txt
 1
```
You run the program a second time, it prints run #2 with a proper line break:
```
 $ ./run-count
 run #2
```
The runcount.txt file should not have 2 followed by a line break after the second run:
```
 $ cat runcount.txt
 2
```

Please test locally using the relevant commands of your operating system to double-check if the behaviour is correct.

This exercise simulates the common pattern of accessing and writing to a configuration file. Sometimes, different programs access the same configuration file, so it is important that they are consistent with the configuration file specification. In the case of this exercise, storing the count as described.

Never call fclose on a NULL pointer, that is bad programming practice and will be specifically checked for in the scoring server: ~~fclose(NULL)~~.

try first: file-write file-read

try next: hello-cmd erro

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