Start the user's configured shell, use -shellname as argv[0]

 * When no command is specified, default to login-mode with the getpwuid()
   shell.

 * Otherwise, allow the -l / --no-login options to override login-mode.

 * Default to pty-mode iff login-mode.

backend/wslbridge-backend.cc

@@ -6,6 +6,7 @@
 #include <netinet/tcp.h>
 #include <pthread.h>
 #include <pty.h>
+#include <pwd.h>
 #include <signal.h>
 #include <stdio.h>
 #include <stdint.h>
@@ -67,6 +68,7 @@ struct ChildParams {
     int cols = -1;
     int rows = -1;
     std::vector<char*> env;
+    std::string prog;
     std::vector<char*> argv;
     std::string cwd;
 };
@@ -200,7 +202,7 @@ static Child spawnChild(const ChildParams &params) {
                 childFailed(SpawnError::Type::ChdirFailed, errno);
             }
         }
-        execvp(params.argv[0], params.argv.data());
+        execvp(params.prog.c_str(), params.argv.data());
         childFailed(SpawnError::Type::ExecFailed, errno);
     }
 
@@ -508,6 +510,7 @@ int main(int argc, char *argv[]) {
     int windowThreshold = -1;
     ChildParams childParams;
     int ptyMode = -1;
+    bool loginMode = false;
 
     const struct option kOptionTable[] = {
         { "pty",            false, &ptyMode,    1 },
@@ -520,7 +523,7 @@ int main(int argc, char *argv[]) {
     };
 
     int ch = 0;
-    while ((ch = getopt_long(argc, argv, "+3:0:1:2:k:c:r:w:t:e:C:", kOptionTable, nullptr)) != -1) {
+    while ((ch = getopt_long(argc, argv, "+3:0:1:2:k:c:r:w:t:e:C:l", kOptionTable, nullptr)) != -1) {
         switch (ch) {
             case 0:
                 // This is returned for the two long options.  getopt_long
@@ -537,6 +540,7 @@ int main(int argc, char *argv[]) {
             case 't': windowThreshold = atoi(optarg); break;
             case 'e': childParams.env.push_back(strdup(optarg)); break;
             case 'C': childParams.cwd = optarg; break;
+            case 'l': loginMode = true; break;
             case 'v':
                 printf("wslbridge-backend " STRINGIFY(WSLBRIDGE_VERSION) "\n");
                 exit(0);
@@ -548,7 +552,27 @@ int main(int argc, char *argv[]) {
         childParams.argv.push_back(argv[i]);
     }
     if (childParams.argv.empty()) {
-        fatal("error: no command line given\n");
+        const char *shell = "/bin/sh";
+        struct passwd *pw = getpwuid(getuid());
+        if (pw == nullptr) {
+            perror("error: getpwuid failed");
+        } else if (pw->pw_shell == nullptr) {
+            fprintf(stderr, "error: getpwuid(...)->pw_shell is NULL\n");
+        } else {
+            shell = pw->pw_shell;
+        }
+        childParams.argv.push_back(strdup(shell));
+    }
+    // XXX: Replace char* args/envstrings with std::string?
+    childParams.prog = childParams.argv[0];
+    if (loginMode) {
+        std::string argv0 = childParams.argv[0];
+        const auto pos = argv0.find_last_of('/');
+        if (pos != std::string::npos) {
+            argv0 = argv0.substr(pos + 1);
+        }
+        argv0 = '-' + argv0;
+        childParams.argv[0] = strdup(argv0.c_str());
     }
     childParams.argv.push_back(nullptr);
 
@@ -598,7 +622,7 @@ int main(int argc, char *argv[]) {
 
     mainLoop(childParams.usePty, controlSocket,
              inputSocket, outputSocket, errorSocket,
-             childParams.argv[0], child, windowParams);
+             childParams.prog.c_str(), child, windowParams);
 
     return 0;
 }

frontend/wslbridge.cc

@@ -619,6 +619,8 @@ static void usage(const char *prog) {
     printf("                An initial '~' indicates the WSL home directory.\n");
     printf("  -e VAR        Copies VAR into the WSL environment.\n");
     printf("  -e VAR=VAL    Sets VAR to VAL in the WSL environment.\n");
+    printf("  -l            Start a login shell.\n");
+    printf("  --no-login    Do not start a login shell.\n");
     printf("  -T            Do not use a pty.\n");
     printf("  -t            Use a pty (as long as stdin is a tty).\n");
     printf("  -t -t         Force a pty (even if stdin is not a tty).\n");
@@ -982,17 +984,22 @@ int main(int argc, char *argv[]) {
     std::string spawnCwd;
     std::string distroGuid;
     enum class TtyRequest { Auto, Yes, No, Force } ttyRequest = TtyRequest::Auto;
+    enum class LoginMode { Auto, Yes, No } loginMode = LoginMode::Auto;
 
     int debugFork = 0;
     int c = 0;
+    if (argv[0][0] == '-') {
+        loginMode = LoginMode::Yes;
+    }
     const struct option kOptionTable[] = {
         { "help",           false, nullptr,     'h' },
         { "debug-fork",     false, &debugFork,  1   },
         { "version",        false, nullptr,     'v' },
         { "distro-guid",    true,  nullptr,     'd' },
+        { "no-login",       false, nullptr,     'L' },
         { nullptr,          false, nullptr,     0   },
     };
-    while ((c = getopt_long(argc, argv, "+e:C:tT", kOptionTable, nullptr)) != -1) {
+    while ((c = getopt_long(argc, argv, "+e:C:tTl", kOptionTable, nullptr)) != -1) {
         switch (c) {
             case 0:
                 // Ignore long option.
@@ -1038,14 +1045,23 @@ int main(int argc, char *argv[]) {
                     fatal("error: the --distro-guid argument '%s' is invalid\n", optarg);
                 }
                 break;
+            case 'l':
+                loginMode = LoginMode::Yes;
+                break;
+            case 'L':
+                loginMode = LoginMode::No;
+                break;
             default:
                 fatal("Try '%s --help' for more information.\n", argv[0]);
         }
     }
 
     const bool hasCommand = optind < argc;
+    if (loginMode == LoginMode::Auto) {
+        loginMode = hasCommand ? LoginMode::No : LoginMode::Yes;
+    }
     if (ttyRequest == TtyRequest::Auto) {
-        ttyRequest = hasCommand ? TtyRequest::No : TtyRequest::Yes;
+        ttyRequest = loginMode == LoginMode::No ? TtyRequest::No : TtyRequest::Yes;
     }
     if (ttyRequest == TtyRequest::Yes && !isatty(STDIN_FILENO)) {
         fprintf(stderr, "Pseudo-terminal will not be allocated because stdin is not a terminal.\n");
@@ -1126,21 +1142,18 @@ int main(int argc, char *argv[]) {
     assert(iRet > 0);
     bashCmdLine.append(buffer.data());
 
+    if (loginMode == LoginMode::Yes) {
+        appendBashArg(bashCmdLine, L"-l");
+    }
     for (const auto &envPair : env.pairs()) {
         appendBashArg(bashCmdLine, L"-e" + envPair.first + L"=" + envPair.second);
     }
     if (!spawnCwd.empty()) {
         appendBashArg(bashCmdLine, L"-C" + mbsToWcs(spawnCwd));
     }
     appendBashArg(bashCmdLine, L"--");
-
-    if (optind == argc) {
-        // No command-line specified.  Use a default one.
-        appendBashArg(bashCmdLine, L"/bin/bash");
-    } else {
-        for (int i = optind; i < argc; ++i) {
-            appendBashArg(bashCmdLine, mbsToWcs(argv[i]));
-        }
+    for (int i = optind; i < argc; ++i) {
+        appendBashArg(bashCmdLine, mbsToWcs(argv[i]));
     }
 
     std::wstring cmdLine;