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CS 456 - Systems Programming
Spring 2024
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Displaying ./code/shellv4/shellbuiltins.c
#include "shell.h"
char *builtin_str[] = {
"cd",
"help",
"curtime",
"hello",
"mycat",
"exit"
};
int (*builtin_func[]) (char **) = {
&shell_cd,
&shell_help,
&shell_curtime,
&shell_hello,
&shell_mycat,
&shell_exit
};
int num_builtins() {
return sizeof(builtin_str) / sizeof(char *);
}
int execute(char **args){
int i;
if (args[0] == NULL) {
// An empty command was entered.
return 1;
}
for (i = 0; i < num_builtins(); i++) {
if (strcmp(args[0], builtin_str[i]) == 0) {
return (*builtin_func[i])(args);
}
}
return launch(args);
}
int argcount(char **args){
int argc = 0;
for(int i = 0; args[i] != NULL; i++)
argc++;
return argc;
}
// shell builtins below
int shell_cd(char **args){
if (args[1] == NULL) {
fprintf(stderr, "shell: expected argument to \"cd\"\n");
} else {
if (chdir(args[1]) != 0) {
perror("shell:");
}
}
return 1;
}
int shell_help(char **args){
printf("Current Builtins\n");
for (int i = 0; i < num_builtins(); i++) {
printf(" %s\n", builtin_str[i]);
}
return 1;
}
int shell_curtime(char **args){
time_t curtime = time(NULL);
char * time_str = ctime(&curtime);
time_str[strlen(time_str)-1] ='\0';
printf("%s\n", time_str);
return 1;
}
int shell_hello(char **args){
printf("Hello, world!\n");
return 1;
}
int shell_mycat(char **args){
if(argcount(args) < 2){
printf("Usage: %s file\n",args[0]);
return 1;
}
int rt;
//open a file
int fd = open(args[1], O_RDONLY);
if(fd == -1){
write(2, "open failed\n",12);
return -1;
}
int size;
struct stat st;
fstat(fd, &st);
size = st.st_size;
char buf[size+1];
rt = read(fd, buf, size);
//printf("Number of bytes read: %d\n", rt);
write(1, buf, rt);
close(fd);
return 1;
}
int shell_exit(char **args){
return 0;
}
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