To compile the information hidden in the comments below the OP's post and my own 2 cents:
#include <stdio.h>
#include <stdlib.h>
// you don't use anything from string.h in your version
//#include <string.h>
// Put simple constants here, for the preprocessor to process
#define LINESIZE 15
// you don't use the arguments, no need to put them here
int main( /*int argc, char *argv[] */ )
{
// such constants are better put into a preprocessor directive
//int LINESIZE = 15; //maximum length of array of characters
int ctr = 0;
// Sorted into three lines (three different types) better to read
// No need to initialize enaString to NULL for malloc/calloc
// It is a good idea to do for realloc(), safes you
// the initial malloc() but you do not use realloc() here
char *enaString;
// (f)getc() and scanf() return an int
int xaraktiras, ret_scanf;
char diaxwristiki[LINESIZE];
// no casting of malloc() in C
enaString = /*(char*) */ malloc(sizeof(char) * LINESIZE + 1);
if (enaString == NULL) //check if the memory has free blocks
{
// use stderr stream for error output
// (sderr might not be available but worth a try)
// UX-tip: use the same language for errors that you
// use for user interaction elsewhere
fprintf(stderr, "error to initillize memory");
// Use the macros from stdlib.h, the return values
// are OS dependent and might not be 0 and 1 respectively
exit(EXIT_FAILURE);
}
// you ask for a word of a certain size or only for a word?
// (My Greek is not very good and Google is of not much help here)
printf("Eisagete xaraktira mikous %d :\n", LINESIZE);
do {
// please be aware the getc() is in most cases implemented
// as a macro, use fgetc() if you are not sure if that is
// a problem (it is not here) because macros might get evaluated
// more than once
xaraktiras = getc(stdin);
// you need to check for EOF somewhere. Here would be a good place
if (xaraktiras == EOF) {
// try it by pressing CTRL+D instead of feeding characters to getc()
fprintf(stderr, "EOF found in getc() loop\n");
// EOF might also indicate an error, see the handling of scanf() below
// We don't bother with it now, we just exit
exit(EXIT_FAILURE);
}
// no need for a cast here
enaString[ctr] = xaraktiras;
// put it after the check, otherwise you have an undefined
// character at enaString[ctr]
// ctr++;
if (ctr == LINESIZE - 1) {
// You offered LINESIZE, have allocated LINESIZE+1, but only
// allow LINESIZE-1
// The user might be disappointed
break;
}
ctr++;
// No casting needed, because the type of a char constant is int
// (yes, that means that things like "char c='STOP'" once worked and you
// were able to look for 0x53544f50 in the memory dump. Some compilers might
// still allow for it but it is not recommended)
} while (xaraktiras != '\n');
// slurp the rest up if there were more characters given
// (check for EOF ommitted here but should be added, of course)
if(xaraktiras != '\n'){
while ((xaraktiras = getc(stdin)) != '\n');
}
// you go up to LINESIZE-1 now, so, together with the replacement of ctr++, it is OK
enaString[ctr + 1] = '\0'; //is this considered undefined behavior?
// don't just dump the painfully gathered characters, print them at least.
// That way you'll find out that you included the '\n', too, which
// might or might not have been your intent
printf("enaString = \"%s\"\n",enaString);
// To free the memory free() needs to know where it is and
// the pointer enaString points to that memory. If you set
// enaString to NULL free() does not know which memory to free
// (worse: free(NULL) is allowed) and the memory
// is left alone, crying, and is unreachable until the program ends,
// a so called "memory leak"
// enaString = NULL;
// free(enaString);
free(enaString);
// I don't know who told you so, but it is indeed a good idea to set
// the pointer to the free'd memory to NULL. Won't do anything here
// but might safe you from a lot of headaches in large programs
enaString = NULL;
printf("eisagete mia leksi diaxwrismou :\n"); //ask the user for another word.
// the variable "diaxwristiki" can hold 15 characters , "%15s" allows for 16, because
// scanf() includes `\0` (EOS, NUL, nul, or whatever the kids call it today), too!
// scanf() returns the number of elements (not characters!) read or EOF.
// for strerror()
#include <string.h>
// for errno
#include <errno.h>
// reset errno, just in case
errno = 0;
if ((ret_scanf = scanf(" %14s", diaxwristiki)) == EOF) {
// It also returns EOF in case of an error, so check for it
if (errno != 0) {
fprintf(stderr, "error in scanf: %s\n", strerror(errno));
exit(EXIT_FAILURE);
}
// try it by pressing CTRL+D instead of feeding characters to scanf()
fprintf(stderr, "EOF triggered by scanf()\n");
// diaxwristiki might contain rubbish at this point, clear it
diaxwristiki[0] = '\0';
}
// no need for adding EOS, scanf() already added it
// diaxwristiki[LINESIZE-1] = '\0';//is this undefined behaviour?
printf("timi diaxwrismou %s\n", diaxwristiki);
// it's "int main()", so return something.
exit(EXIT_SUCCESS);
}
