====== Learning C ======


  * [[http://www.librarything.fr/work/3600740/book/62075147 | The C Programming Language]].


====== Simple examples ======
===== Hello World =====
<code c>
/* Hello World program */

#include<stdio.h>

main()
{
    printf("Hello World");
}
</code>

Compile and run the program:
<code bash>
$ gcc -Wall hello.c -o hello.out
hello.c:6: warning: return type defaults to ‘int’
hello.c: In function ‘main’:
hello.c:10: warning: control reaches end of non-void function

$ ./hello.out 
Hello World
</code>


===== Increment a number =====
<code c>
#include "stdio.h"

char  line[100];
int   value;

int main()
{
    printf("Enter a value:");
    fgets(line, sizeof(line), stdin);
    sscanf(line, "%d", &value);

    printf("Inc: %d\n", value + 1);

    return 0;
}
</code>

<code bash>
$ gcc -Wall test1.c 
cedric@debian:~$ ./a.out 
Enter a value:41
Inc: 42
</code>

==== Equivalent in python ====
<code python>
>>> def inc():
...     value = raw_input("Enter a value:")
...     print "Inc:", int(value)+1
... 
>>> inc()
Enter a value:41
Inc: 42
</code>



===== Read a file =====
<code c>
#include <stdio.h>   /* required for file operations */

FILE *fr;            /* declare the file pointer */

main()
{
   char line[1024];
   fr = fopen ("./file.txt", "rt");  /* open the file for reading */
   /* "rt" means open the file for reading text */

   while(fgets(line, 1024, fr) != NULL)
   {
         printf ("%s\n", line);
   }
   fclose(fr);  /* close the file prior to exiting the routine */
}
</code>

==== Equivalent in python ====
<code python>
for line in open("./file.txt", "r"):
    print line
</code>