#include <stdio.h>
#include <string.h>
 
int main ()
{	char buffer [32], letra; int i=0, cont=0;
	printf ("Cadena: "); read (0, buffer, 32); for (i=0; buffer[i] != '\0' && buffer[i] != '\n' && i!=32; i++); buffer [i]='\0';
	printf ("Letra: "); read (0, &letra, 1);
	for (i=0; i<strlen (buffer); i++) if (buffer[i]==letra) cont++;
	printf ("La letra %c aparace %d veces\n", letra, cont); return 0;
}
 

#include <stdio.h>
 
int lenght (char *s)
{	int i;
	for (i=0; s [i] != '\0'; i++);
	return i;
}
 
int compare(char a[], char b[])
{	int i;
	if (lenght (a) != lenght (b)) return 1;
	for (i=0; i<lenght (a); i++) if (a[i] != b[i]) return 1;
	return 0;
}
 
int main()
{	printf("Introduce la clave: ");
	char var [32]; char ok [] = "hola"; int i;
	fgets (var, 32, stdin); for (i=0; var [i]!='\n' && i<32; i++); var [i]='\0';
	if (compare(var, ok) == 0)	printf("Enhorabuena!\n");
	else				printf("Pringao\n");
	return 0;
}
 

int lenght (char *s)
{	int i;
	for (i=0; s [i] != '\0'; i++);
	return i;
}
 
int compare(char a[], char b[])
{	int i;
	if (lenght (a) != lenght (b)) return 1;
	for (i=0; i<lenght (a); i++) if (a[i] != b[i]) return 1;
	return 0;
}
 
int main()
{	write (1, "Password: ", 10);
	char var [32]; char ok [] = "hola"; int i;
	read (1, var, 32); for (i=0; var [i]!='\n' && i<32; i++); var [i]='\0';
	if (compare(var, ok) == 0)	write (1, "OK!\n\n", 5);
	else				write (1, "BAD\n\n", 5);
	return 0;
} 
 

#include <stdio.h>
#include <fcntl.h>
 
int main (int argc, char *argv [])
{	if (argc != 2) { printf ("Use: %s <file>\n", argv [0]); return 1; }
	int fd; char car=0;
	if ((fd=open (argv [1], O_CREAT|O_APPEND|O_WRONLY, 0700)) == -1) { perror ("Opening file"); return 1; }
	while (car != '\n') { read (1, &car, 1); write (fd, &car, 1); }
	close (fd); return 0;
}
 

[sagrini@Arch Desktop]$ gcc -o code code.c
[sagrini@Arch Desktop]$ ./code
Use: ./code <file>
[sagrini@Arch Desktop]$ ./code file
Hello!
[sagrini@Arch Desktop]$ cat file
Hello!
[sagrini@Arch Desktop]$