#include <stdio.h>
#include <stdlib.h>
int main (int argc, char *argv[]) {
printf ("Pruebe a ejecutar este programa como 'programa ls -l'\n");
int i;
printf ("\n Ejecutando el programa (%s). Sus argumentos son: \n", argv[0]);
for (i=0; i<argc; i++)
printf (" argv[%d]: %s \n",i,argv[i]);
sleep (2);
/* La familia de funciones exec reemplaza la imagen del proceso
* en curso con una nueva. Si cualquiera de las funciones exec
* regresa, es que ha ocurrido un error.
* Por legibilidad ponemos el código en una claúsula if
* pero bastaría:
* execvp (orden, params, 0);
* printf("Error\n");
* exit (1);
* Ya que si llegamos a printf es porque execvp no ha conseguido
* cambiar la imagen de memoria
* */
if (execvp (argv[1],&argv[1])<0) {
printf("Error en la invocacion\n");
exit (1);
}
// Terminamos
return 0;
}
http://www2.its.strath.ac.uk/courses/c/
http://www.digilife.be/quickreferences/quickrefs.htm
http://en.wikipedia.org/wiki/C_programming_language
http://guimi.net/index.php?pag_id=cmsxp0...s.html#man
/* ----------------------------------------------------------------- */
/* PROGRAM shell.c */
/* This program reads in an input line, parses the input line */
/* into tokens, and use execvp() to execute the command. */
/* ----------------------------------------------------------------- */
#include <stdio.h>
#include <sys/types.h>
/* ----------------------------------------------------------------- */
/* FUNCTION parse: */
/* This function takes an input line and parse it into tokens. */
/* It first replaces all white spaces with zeros until it hits a */
/* non-white space character which indicates the beginning of an */
/* argument. It saves the address to argv[], and then skips all */
/* non-white spaces which constitute the argument. */
/* ----------------------------------------------------------------- */
void parse(char *line, char **argv)
{
while (*line != '\0') { /* if not the end of line ....... */
while (*line == ' ' || *line == '\t' || *line == '\n')
*line++ = '\0'; /* replace white spaces with 0 */
*argv++ = line; /* save the argument position */
while (*line != '\0' && *line != ' ' &&
*line != '\t' && *line != '\n')
line++; /* skip the argument until ... */
}
*argv = '\0'; /* mark the end of argument list */
}
/* ----------------------------------------------------------------- */
/* FUNCTION execute: */
/* This function receives a commend line argument list with the */
/* first one being a file name followed by its arguments. Then, */
/* this function forks a child process to execute the command using */
/* system call execvp(). */
/* ----------------------------------------------------------------- */
void execute(char **argv)
{
pid_t pid;
int status;
if ((pid = fork()) < 0) { /* fork a child process */
printf("*** ERROR: forking child process failed\n");
exit(1);
}
else if (pid == 0) { /* for the child process: */
if (execvp(*argv, argv) < 0) { /* execute the command */
printf("*** ERROR: exec failed\n");
exit(1);
}
}
else { /* for the parent: */
while (wait(&status) != pid) /* wait for completion */
;
}
}
/* ----------------------------------------------------------------- */
/* The main program starts here */
/* ----------------------------------------------------------------- */
void main(void)
{
char line[1024]; /* the input line */
char *argv[64]; /* the command line argument */
while (1) { /* repeat until done .... */
printf("Shell -> "); /* display a prompt */
gets(line); /* read in the command line */
printf("\n");
parse(line, argv); /* parse the line */
if (strcmp(argv[0], "exit") == 0) /* is it an "exit"? */
exit(0); /* exit if it is */
execute(argv); /* otherwise, execute the command */
}
}