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Learning C

Simple examples

Hello World

/* Hello World program */
    printf("Hello World");

Compile and run the program:

$ 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

Increment a number

#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;
$ gcc -Wall test1.c 
cedric@debian:~$ ./a.out 
Enter a value:41
Inc: 42

Equivalent in python

>>> def inc():
...     value = raw_input("Enter a value:")
...     print "Inc:", int(value)+1
>>> inc()
Enter a value:41
Inc: 42

Read a file

#include <stdio.h>   /* required for file operations */
FILE *fr;            /* declare the file pointer */
   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 */

Equivalent in python

for line in open("./file.txt", "r"):
    print line
cs_lang/c.txt · Last modified: 2012/09/30 23:32 by cedric