initial

Makefile

@@ -0,0 +1,5 @@
+CC = gcc
+CFLAGS = -Wall -Wextra -std=c99 -pedantic -g
+
+finger: finger.c
+	$(CC) $(CFLAGS) $< -o $@

finger.c

@@ -0,0 +1,85 @@
+#include <stdio.h>
+#include <stdlib.h>
+#include <string.h>
+#include <strings.h>
+#include <unistd.h>
+#include <netdb.h>
+#include <sys/socket.h>
+
+#define PORT 79
+
+void
+die(char *msg)
+{
+    fprintf(stderr, "%s\n", msg);
+    exit(1);
+}
+
+void
+read_server_response(int sockfd)
+{
+    char c;
+    while (read(sockfd, &c, 1) != 0) {
+        if (c != '\r')
+            putchar(c);
+    }
+}
+
+void
+finger_serverinfo(int sockfd)
+{
+    write(sockfd, "\r\n", 2);
+
+    read_server_response(sockfd);
+}
+
+void
+finger_user(int sockfd, char *username)
+{
+    write(sockfd, username, strlen(username));
+    write(sockfd, "\r\n", 2);
+
+    read_server_response(sockfd);
+}
+
+int
+main(int argc, char *argv[])
+{
+    /* argument handling */
+    if (argc < 2 || argc > 3)
+        die("usage: finger [user] server");
+
+    char *servername, *user = NULL;
+    if (argc == 2) {
+        servername = argv[1];
+    }
+    else {
+        servername = argv[2];
+        user = argv[1];
+    }
+
+    struct sockaddr_in servaddr;
+
+    int sockfd = socket(AF_INET, SOCK_STREAM, 0);
+    if (sockfd == -1)
+        die("Couldn't create socket.");
+
+    struct hostent *he = gethostbyname(servername);
+    if (he == NULL)
+        die("Couldn't get host.");
+
+    bzero(&servaddr, sizeof(servaddr));
+    servaddr.sin_family = AF_INET;
+    servaddr.sin_addr = *((struct in_addr *) he->h_addr_list[0]);
+    servaddr.sin_port = htons(PORT);
+
+    if (connect(sockfd, (struct sockaddr*)&servaddr, sizeof(servaddr)) != 0)
+        die("Couldn't connect to server.");
+
+    if (user)
+        finger_user(sockfd, user);
+    else
+        finger_serverinfo(sockfd);
+
+    close(sockfd);
+}