init: initial implementation

extras/init/Makefile

@@ -0,0 +1,13 @@
+XCC=x86_64-astral-gcc
+
+all: init
+
+init: main.o
+	$(XCC) $(LDFLAGS) -o $@ $<
+
+%.o: %.c
+	$(XCC) -c $(CFLAGS) -o $@ $<
+
+install:
+	mkdir -p $(DESTDIR)/sbin/
+	mv init $(DESTDIR)/sbin/init

extras/init/main.c

@@ -0,0 +1,147 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <errno.h>
+#include <sys/stat.h>
+#include <string.h>
+#include <unistd.h>
+#include <sys/types.h>
+#include <sys/wait.h>
+
+FILE* openordie(const char* name, const char* mode){
+	
+	FILE* file = fopen(name, mode);
+
+	if(!file){
+		printf("init: Failed to open /etc/initlist: %s\n", strerror(errno));
+		exit(1);
+	}
+
+	return file;
+}
+
+void oom(){
+	printf("init: %s", strerror(ENOMEM));
+	exit(1);
+}
+
+void printwelcome(FILE* welcome){
+	char buff[4096];
+
+	while(1){
+		
+		size_t readc = fread(buff, 1, 4095, welcome);
+
+		if(readc == 0)
+			break;
+		
+		buff[readc] = '\0';
+
+		printf("%s", buff);
+
+	}
+
+	printf("\n");
+	
+}
+
+int main(int argc, char* argv[]){
+
+	FILE* shell = openordie("/etc/init/shell", "r");
+	FILE* shellenv = openordie("/etc/init/shellenv", "r");
+	FILE* welcome = openordie("/etc/init/welcome", "r");
+
+	printwelcome(welcome);
+	
+	fclose(welcome);
+	
+	char readbuff[4096];	
+	size_t readc = fread(readbuff, 4095, 1, shell);
+
+	if(ferror(shell)){
+		printf("init: Failed to read from /etc/init/shell: %s\n", strerror(errno));
+		exit(1);
+	}
+	
+	void* shellbuff = strtok(readbuff, "\n");
+
+	char* name = strtok(shellbuff, " ");
+	
+	// test if shell exists
+	
+	struct stat st;
+
+	if(stat(name, &st) == -1){
+		printf("init: stat failed on %s: %s\n", name, strerror(errno));
+		exit(1);
+	}
+	
+	char* token = name;
+	size_t tokenc = 0;
+
+	char** args = malloc(1); // initialize this
+
+
+	while(token){
+		args = realloc(args, ++tokenc*sizeof(char*));
+		if(!args)
+			oom();
+
+		args[tokenc-1] = malloc(strlen(token)+1);
+
+		if(!args[tokenc-1])
+			oom();
+
+		strcpy(args[tokenc-1], token);
+
+		token = strtok(NULL, " ");
+		
+	}
+		
+	args = realloc(args, (tokenc+1)*sizeof(char*)); // for null terminator
+	if(!args)
+		oom();
+	
+	args[tokenc] = NULL;
+	
+	char* envbuff;
+	size_t envsize;
+
+	if(getline(&envbuff, envsize, shellenv) == -1){
+		if(ferror(shellenv)){
+			printf("init: getline failed on shellenv: %s\n", strerror(errno));
+			exit(1);
+		}
+		else envbuff = NULL;
+	}
+
+
+	while(envbuff){
+		
+		if(putenv(envbuff)) oom();
+
+		if(getline(&envbuff, envsize, shellenv) == -1 && ferror(shellenv)){
+			printf("init: getline failed on shellenv: %s\n", strerror(errno));
+			exit(1);
+		}
+	}
+
+	// execute shell
+	
+	pid_t shellpid = fork();
+
+	if(shellpid == -1){
+		printf("init: fork failed: %s\n", strerror(errno));
+		exit(1);
+	}
+	
+	if(shellpid == 0){
+		execv(name, args);
+		printf("init: exec failed: %s\n", strerror(errno));
+		exit(1);
+	}
+	
+	int status;
+
+	for(;;) waitpid(-1, &status, 0);
+
+}