user: implement mlibc as the libc, finally.

It's finally done..

Signed-off-by: kaguya <vpshinomiya@protonmail.com>

user/include/mlibc/tests/posix/usershell.c

@@ -0,0 +1,63 @@
+#include <unistd.h>
+#include <assert.h>
+#include <string.h>
+#include <stdio.h>
+
+static void testfor(const char *expected, char *shell, int *count) {
+	if (strcmp(shell, expected) == 0)
+		*count += 1;
+}
+
+#define BUFFER_SIZE (1024 * 512)
+
+int main(void) {
+	setusershell();
+
+	FILE *f = fopen("/etc/shells", "r");
+	if (f == NULL) {
+		/* /etc/shells file is unreadable, test for the existance of /bin/sh and /bin/csh */
+		char *shell = getusershell();
+		int csh = 0;
+		int sh = 0;
+
+		testfor("/bin/sh", shell, &sh);
+		testfor("/bin/csh", shell, &csh);
+
+		shell = getusershell();
+		assert(shell);
+
+		testfor("/bin/sh", shell, &sh);
+		testfor("/bin/csh", shell, &csh);
+
+		assert(sh == 1 && csh == 1);
+		assert(getusershell() == NULL);
+	} else {
+		/* /etc/shells is there, read the whole file into a buffer and change all '\n's to '\0'. */
+		char buffer[BUFFER_SIZE + 1];
+		int nbytes = fread(buffer, 1, BUFFER_SIZE, f);
+		buffer[nbytes] = '\0';
+
+		for (int i = 0; i < nbytes; ++i) {
+			if (buffer[i] == '\n')
+				buffer[i] = '\0';
+		}
+
+		/* loop through each shell and make sure the result is right */
+		char *shell = buffer;
+		while (shell < &buffer[nbytes]) {
+			char *usershell = getusershell();
+			while (usershell && *usershell == '#')
+				usershell = getusershell();
+
+			while (*shell == '#')
+				shell += strlen(shell) + 1;
+
+			assert(strcmp(shell, usershell) == 0);
+			shell += strlen(shell) + 1;
+		}
+	}
+
+	endusershell();
+
+	return 0;
+}