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#include <stdio.h>
main()
{
char buf[1024];
char *args[64];
for (;;) {
/*
* Prompt for and read a command.
*/
printf("Command: ");
if (gets(buf) == NULL) {
printf("\n");
exit(0);
}
/*
* Split the string into arguments.
*/
parse(buf, args);
/*
* Execute the command.
*/
execute(args);
}
}
/*
* parse--split the command in buf into
* individual arguments.
*/
parse(buf, args)
char *buf;
char **args;
{
while (*buf != NULL) {
/*
* Strip whitespace. Use nulls, so
* that the previous argument is terminated
* automatically.
*/
while ((*buf == ' ') || (*buf == '\t'))
*buf++ = NULL;
/*
* Save the argument.
*/
*args++ = buf;
/*
* Skip over the argument.
*/
while ((*buf != NULL) && (*buf != ' ') && (*buf != '\t'))
buf++;
}
*args = NULL;
}
/*
* execute--spawn a child process and execute
* the program.
*/
execute(args)
char **args;
{
int pid, status;
/*
* Get a child process.
*/
if ((pid = fork()) < 0) {
perror("fork");
exit(1);
}
/*
* The child executes the code inside the if.
*/
if (pid == 0) {
execvp(*args, args);
perror(*args);
exit(1);
}
/*
* The parent executes the wait.
*/
while (wait(&status) != pid)
/* empty */ ;
}
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