INI files

INI files contain data in basic text format

The structure of INI file is the following:

[section1]
key1 = value1
key2 = value2
key3 = value3

; comment
[section2]
key4 = value4
key5 = value5
key6 = value6

There are:
- Sections with names between brackets
- Pairs of keys and values
- Empty lines
- Comments

Project

Write a C program to parse INI files using only C standard library
You can work in pairs
Send the source codes via eKursy
Hints:
- Compile with -Wall -Wextra flags and fix all warnings
- Run against Valgrind to make sure there are no memory errors/leaks

Requirements for 3.0

The program should accept two command line parameters in the format:
```
$ ./program PATH-TO-INI-FILE.ini section.key
```
For example:
```
$ ./program test.ini data.velocity
```
Program must print out the value of key in the given section
For the example above, the program has to print out value under velocity key in [data] section
You can assume the following limits:
- Number of sections < 30
- Length of section name < 30
- Length of key < 30
- Length of value < 30

Useful resources

Main function, command line parameter handling
File input/output
fopen() reference and man page
fclose() reference and man page
fgets() reference and man page
fscanf() reference and man page

Requirements for 3.5

Program must detect a missing section and print out dedicated message e.g. Failed to find section [data]
Program must detect a missing key in a present section e.g. Failed to find key "velocity" in section [data]

Requirements for 4.0

Parse the data into well defined structures e.g. struct section { ... };
Program must detect invalid identifiers in INI file (section names and keys) i.e. those which contain characters other than letters, digits and dashes (the - character)

Useful resources

struct declarations
isalnum() reference and man page

Requirements for 4.5

The limits from the 3.0 requirements are no longer valid
Therefore, program must accept arbitrary INI files with section name, key or value of any length (without compile-time limit)

Useful resources

Dynamic memory management

Requirements for 5.0

Program must distinguish types of values between strings and numbers
Program must be able to understand simple expressions given by the following command line parameters:
```
$ ./program PATH-TO-INI-FILE.ini expression "distance.velocity * travel.time"
```
The rules for expression evaluation are the following:
- For numbers, support addition (+ operator), subtraction (- operator), multiplication (* operator) and division (/ operator)
- For strings, support concatenation (+ operator)
- Expression involving operands of different types is invalid (detect it and print out a message) e.g. distance.velocity + text.message is invalid
- Usage of operators -, * and / for string type operands is also invalid e.g. text.hello * text.world

Useful resources

strcmp() reference and man page
strtok() reference and man page
strcpy() reference and man page
strcat() reference and man page

Example files

Exercises to practice

Write a cat-like utility, which opens a file and prints its content to the terminal

$ cat input.txt
Intelligence forged from circuits and code,
A mind of silicon, a new kind of ode.

$ ./program input.txt
Intelligence forged from circuits and code,
A mind of silicon, a new kind of ode.

Write a simple grep-like utility, which opens a file and prints lines containing a given word

$ cat input.txt
Infinite knowledge at its core,
Capable of so much more,
A creation to marvel and admire,
AI's greatness shall never expire.

$ ./program input.txt admire
A creation to marvel and admire,

Write a program, that will read numeric content and calculate sums of each row

$ cat input.txt
58  32  49  22
93  76  68  85
14  25  17  35
42  19  11  70
56  81  37  98

$ ./program input.txt
161
322
91
142
272