我写了简单的wlan管理工具。它使用system（）运行iproute2 / iw / wpa_supplicant / dhcpcd来连接到接入点。现在我想将它改进为比运行外部命令更好的方法。有些人说你永远不应该使用system（），因为在C中总有更好的方法。
我探索了wicd，看起来它纯粹是通过执行和解析外部命令来工作的。 NetworkManager更复杂，似乎使用其他一些方法。我知道最好用外部库完成。如果是这种情况，我想知道我应该寻找哪些库。作为旁注，如果我在代码设计中做出了糟糕的选择，那将会很高兴。
ccwm.c
#include <stdlib.h>
#include <stdio.h>
#include <unistd.h>
#include <sys/types.h>
#include <string.h>
char **global_argv;
void usage() {
printf("Usage: %s [options] -o/-a/-w/-W\n\n", global_argv[0]);
puts("-h Show help\n");
puts("-i [interface] Set interface (default: wlan0)");
puts("-e [ssid] Set SSID");
puts("-f [freq] Set frequency");
puts("-k [key] Set key/passphrase\n");
puts("-s Scan access points");
puts("-S Scan access points verbosely");
puts("-I Show interface info\n");
puts("-o Connect to ESS access point");
puts("-a Connect to IBSS access point");
puts("-w Connect to WEP encrypted access point");
puts("-W Connect to WPA encrypted access point");
}
void ifup(char *ifname) {
char *cmdline = "";
cmdline = malloc(36);
size_t s1 = strlen(ifname);
snprintf(cmdline, s1+16, "ip link set %s up", ifname);
system(cmdline);
free(cmdline);
}
void scan(char *ifname, int type) {
char *cmdline = "";
cmdline = malloc(33);
size_t s1 = strlen(ifname);
if (type == 0) {
snprintf(cmdline, s1+31, "iw dev %s scan | awk -f scan.awk", ifname);
system(cmdline);
}
else {
snprintf(cmdline, s1+13, "iw dev %s scan", ifname);
system(cmdline);
}
free(cmdline);
}
void info(char *ifname) {
char *cmdline = "";
cmdline = malloc(43);
size_t s1 = strlen(ifname);
snprintf(cmdline, s1+13, "iw dev %s info", ifname);
system(cmdline);
snprintf(cmdline, s1+13, "iw dev %s link", ifname);
system(cmdline);
snprintf(cmdline, s1+23, "iw dev %s get power_save", ifname);
system(cmdline);
free(cmdline);
}
void connect(char *ifname, char *essid, char *freq, char *key, int type) {
system("killall dhcpcd 2> /dev/null");
char *cmdline = "";
cmdline = malloc(100);
size_t s1 = strlen(ifname);
size_t s2 = strlen(essid);
size_t s3 = strlen(freq);
size_t s4 = strlen(key);
if (type < 3) {
snprintf(cmdline, s1+25, "iw dev %s set type managed", ifname);
system(cmdline);
}
else {
snprintf(cmdline, s1+22, "iw dev %s set type ibss", ifname);
system(cmdline);
}
if (type == 0) {
snprintf(cmdline, s1+s2+20, "iw dev %s connect -w %s", ifname, essid);
system(cmdline);
snprintf(cmdline, s1+8, "dhcpcd %s", ifname);
system(cmdline);
}
else if (type == 1) {
snprintf(cmdline, s1+s2+s4+26, "iw dev %s connect -w %s keys %s", ifname, essid, key);
system(cmdline);
snprintf(cmdline, s1+8, "dhcpcd %s", ifname);
system(cmdline);
}
else if (type == 2) {
snprintf(cmdline, s1+s2+s4+45, "wpa_supplicant -B -i %s -c <(wpa_passphrase %s %s)",
ifname, essid, key);
system(cmdline);
snprintf(cmdline, s1+8, "dhcpcd %s", ifname);
system(cmdline);
}
else {
snprintf(cmdline, s1+s2+s3+20, "iw dev %s ibss join %s %s", ifname, essid, freq);
system(cmdline);
snprintf(cmdline, s1+8, "dhcpcd %s", ifname);
system(cmdline);
}
free(cmdline);
}
int main(int argc, char *argv[]) {
global_argv = argv;
int opt;
char *ifname = "wlan0";
char *essid = "";
char *freq = "";
char *key = "";
uid_t uid=getuid();
if (uid != 0) {
puts("\nThis program needs to be run with root privileges!\n");
}
if (argc <= 1) {
usage();
}
while ((opt = getopt(argc, argv, "IsSowWahi:e:f:k:")) != -1) {
switch (opt) {
case 'i':
ifname = optarg;
break;
case 'e':
essid = optarg;
break;
case 'f':
freq = optarg;
break;
case 'k':
key = optarg;
break;
case 'I':
ifup(ifname);
info(ifname);
break;
case 's':
ifup(ifname);
scan(ifname, 0);
break;
case 'S':
ifup(ifname);
scan(ifname, 1);
break;
case 'o':
if (essid[0] == '\0') {
printf("You must specify ssid!\n");
break;
}
ifup(ifname);
connect(ifname, essid, freq, key, 0);
break;
case 'w':
if (essid[0] == '\0' || key[0] == '\0') {
printf("You must specify ssid and key!\n");
break;
}
ifup(ifname);
connect(ifname, essid, freq, key, 1);
break;
case 'W':
if (essid[0] == '\0' || key[0] == '\0') {
printf("You must specify ssid and passphrase!\n");
break;
}
ifup(ifname);
connect(ifname, essid, freq, key, 2);
break;
case 'a':
if (essid[0] == '\0' || freq[0] == '\0') {
printf("You must specify ssid and freq!\n");
break;
}
ifup(ifname);
connect(ifname, essid, freq, key, 3);
break;
case 'h':
default:
usage();
break;
}
}
return 0;
}
scan.awk
/^BSS / {
MAC = $2
wifi[MAC]["enc"] = "Open"
}
$1 == "SSID:" {
wifi[MAC]["SSID"] = $2
}
$1 == "freq:" {
wifi[MAC]["freq"] = $2
}
$1 == "signal:" {
wifi[MAC]["sig"] = $2 " " $3
}
$1 == "capability:" {
wifi[MAC]["type"] = $2
}
$1 == "WPA:" {
wifi[MAC]["enc"] = "WPA"
}
$1 == "WEP:" {
wifi[MAC]["enc"] = "WEP"
}
END {
for (w in wifi) {
if ( i++ > 0 ) { printf "\n" }
printf "SSID: %s\nType: %s\nFrequency: %s\nSignal: %s\nEncryption: %s\n"\
,wifi[w]["SSID"],wifi[w]["type"],wifi[w]["freq"],wifi[w]["sig"],wifi[w]["enc"]
}
}