Add a -C option that changes the directory just before calling exec

If the argument is '~' or starts with '~/', then the '~' is replaced with the content of the HOME environment variable. Implements #2
rprichard · Sep 28, 2016 · fff7828 · fff7828
1 parent 3dd52c8
commit fff7828
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Showing 3 changed files with 63 additions and 18 deletions.
diff --git a/backend/wslbridge-backend.cc b/backend/wslbridge-backend.cc
@@ -54,12 +54,21 @@ static int connectSocket(int port, const std::string &key) {
     return s;
 }
 
+static std::string resolveCwd(const std::string &cwd) {
+    if (cwd == "~" || cwd.substr(0, 2) == "~/") {
+        const auto home = getenv("HOME") ?: "";
+        return home + cwd.substr(1);
+    }
+    return cwd;
+}
+
 struct ChildParams {
     bool usePty = false;
     int cols = -1;
     int rows = -1;
     std::vector<char*> env;
     std::vector<char*> argv;
+    std::string cwd;
 };
 
 struct Child {
@@ -174,29 +183,36 @@ static Child spawnChild(const ChildParams &params) {
 
     } else if (pid == 0) {
         // forked process
+        const auto childFailed = [&](SpawnError::Type type, int savedErrno) {
+            const SpawnError err = {
+                type,
+                bridgedError(savedErrno)
+            };
+            writeAllRestarting(spawnErrPipe.write.fd(), &err, sizeof(err));
+            _exit(1);
+        };
         spawnErrPipe.read.close();
         for (const auto &setting : params.env) {
             putenv(setting);
         }
+        if (!params.cwd.empty()) {
+            if (chdir(resolveCwd(params.cwd).c_str()) != 0) {
+                childFailed(SpawnError::Type::ChdirFailed, errno);
+            }
+        }
         execvp(params.argv[0], params.argv.data());
-        const int err = errno;
-        writeAllRestarting(spawnErrPipe.write.fd(), &err, sizeof(err));
-        abort();
+        childFailed(SpawnError::Type::ExecFailed, errno);
     }
 
     UniqueFd masterFd(masterFdRaw);
 
     spawnErrPipe.write.close();
 
-    int execErrno = -1;
-    if (readAllRestarting(spawnErrPipe.read.fd(), &execErrno, sizeof(execErrno))) {
+    SpawnError err = {};
+    if (readAllRestarting(spawnErrPipe.read.fd(), &err, sizeof(err))) {
         // The child exec call failed.
         int dummy = 0;
         waitpid(pid, &dummy, 0);
-        const SpawnError err = {
-            SpawnError::Type::ExecFailed,
-            bridgedError(execErrno)
-        };
         Child ret;
         ret.spawnError = err;
         return ret;
@@ -489,7 +505,7 @@ 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:", kOptionTable, nullptr)) != -1) {
+    while ((ch = getopt_long(argc, argv, "+3:0:1:2:k:c:r:w:t:e:C:", kOptionTable, nullptr)) != -1) {
         switch (ch) {
             case 0:
                 // This is returned for the two long options.  getopt_long
@@ -505,6 +521,7 @@ int main(int argc, char *argv[]) {
             case 'w': windowSize = atoi(optarg); break;
             case 't': windowThreshold = atoi(optarg); break;
             case 'e': childParams.env.push_back(strdup(optarg)); break;
+            case 'C': childParams.cwd = optarg; break;
             case 'v':
                 printf("wslbridge-backend " STRINGIFY(WSLBRIDGE_VERSION) "\n");
                 exit(0);

diff --git a/common/SocketIo.h b/common/SocketIo.h
@@ -72,7 +72,12 @@ struct BridgedError {
 };
 
 struct SpawnError {
-    enum class Type : int32_t { Success, ForkPtyFailed, ExecFailed } type;
+    enum class Type : int32_t {
+        Success = 0,
+        ForkPtyFailed,
+        ExecFailed,
+        ChdirFailed,
+    } type;
     BridgedError error;
 };
 

diff --git a/frontend/wslbridge.cc b/frontend/wslbridge.cc
@@ -280,6 +280,7 @@ void TerminalState::exitCleanly(int exitStatus) {
 static TerminalState g_terminalState;
 
 struct IoLoop {
+    std::string spawnCwd;
     std::string spawnProgName;
     bool usePty = false;
     std::mutex mutex;
@@ -365,10 +366,18 @@ static void handlePacket(IoLoop *ioloop, const Packet &p) {
         }
         case Packet::Type::SpawnFailed: {
             std::string msg;
-            if (p.u.spawnError.type == SpawnError::Type::ForkPtyFailed) {
-                msg = "error: forkpty failed: ";
-            } else {
-                msg = "error: could not start '" + ioloop->spawnProgName + "': ";
+            switch (p.u.spawnError.type) {
+                case SpawnError::Type::ForkPtyFailed:
+                    msg = "error: forkpty failed: ";
+                    break;
+                case SpawnError::Type::ChdirFailed:
+                    msg = "error: could not chdir to '" + ioloop->spawnCwd + "': ";
+                    break;
+                case SpawnError::Type::ExecFailed:
+                    msg = "error: could not exec '" + ioloop->spawnProgName + "': ";
+                    break;
+                default:
+                    assert(false && "Unhandled SpawnError type");
             }
             msg += errorString(p.u.spawnError.error);
             g_terminalState.fatal("%s\n", msg.c_str());
@@ -381,11 +390,13 @@ static void handlePacket(IoLoop *ioloop, const Packet &p) {
     }
 }
 
-static void mainLoop(const std::string &spawnProgName,
+static void mainLoop(const std::string &spawnCwd,
+                     const std::string &spawnProgName,
                      bool usePty, int controlSocketFd,
                      int inputSocketFd, int outputSocketFd, int errorSocketFd,
                      TermSize termSize) {
     IoLoop ioloop;
+    ioloop.spawnCwd = spawnCwd;
     ioloop.spawnProgName = spawnProgName;
     ioloop.usePty = usePty;
     ioloop.controlSocketFd = controlSocketFd;
@@ -599,6 +610,8 @@ static void usage(const char *prog) {
     printf("Runs a program within a Windows Subsystem for Linux (WSL) pty\n");
     printf("\n");
     printf("Options:\n");
+    printf("  -C WSLDIR     Changes the working directory to WSLDIR first.\n");
+    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("  -T            Do not use a pty.\n");
@@ -741,6 +754,7 @@ int main(int argc, char *argv[]) {
     g_wakeupFd = new WakeupFd();
 
     Environment env;
+    std::string spawnCwd;
     enum class TtyRequest { Auto, Yes, No, Force } ttyRequest = TtyRequest::Auto;
 
     int debugFork = 0;
@@ -751,7 +765,7 @@ int main(int argc, char *argv[]) {
         { "version",        false, nullptr,     'v' },
         { nullptr,          false, nullptr,     0   },
     };
-    while ((c = getopt_long(argc, argv, "+e:tT", kOptionTable, nullptr)) != -1) {
+    while ((c = getopt_long(argc, argv, "+e:C:tT", kOptionTable, nullptr)) != -1) {
         switch (c) {
             case 0:
                 // Ignore long option.
@@ -769,6 +783,12 @@ int main(int argc, char *argv[]) {
                 }
                 break;
             }
+            case 'C':
+                spawnCwd = optarg;
+                if (spawnCwd.empty()) {
+                    fatal("error: the -C option requires a non-empty string argument");
+                }
+                break;
             case 'h':
                 usage(argv[0]);
                 break;
@@ -871,6 +891,9 @@ int main(int argc, char *argv[]) {
     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"--");
 
     std::string spawnProgName;
@@ -944,7 +967,7 @@ int main(int argc, char *argv[]) {
 
     backendStarted = true;
 
-    mainLoop(spawnProgName,
+    mainLoop(spawnCwd, spawnProgName,
              usePty, controlSocketC,
              inputSocketC, outputSocketC, errorSocketC,
              initialSize);