source: downloads/tcl8.5.2/unix/tclUnixPipe.c @ 25

/*
 * tclUnixPipe.c --
 *
 *      This file implements the UNIX-specific exec pipeline functions, the
 *      "pipe" channel driver, and the "pid" Tcl command.
 *
 * Copyright (c) 1991-1994 The Regents of the University of California.
 * Copyright (c) 1994-1997 Sun Microsystems, Inc.
 *
 * See the file "license.terms" for information on usage and redistribution of
 * this file, and for a DISCLAIMER OF ALL WARRANTIES.
 *
 * RCS: @(#) $Id: tclUnixPipe.c,v 1.42 2008/03/14 16:32:52 rmax Exp $
 */

#include "tclInt.h"

#ifdef USE_VFORK
#define fork vfork
#endif

/*
 * The following macros convert between TclFile's and fd's. The conversion
 * simple involves shifting fd's up by one to ensure that no valid fd is ever
 * the same as NULL.
 */

#define MakeFile(fd)    ((TclFile)INT2PTR(((int)(fd))+1))
#define GetFd(file)     (PTR2INT(file)-1)

/*
 * This structure describes per-instance state of a pipe based channel.
 */

typedef struct PipeState {
    Tcl_Channel channel;        /* Channel associated with this file. */
    TclFile inFile;             /* Output from pipe. */
    TclFile outFile;            /* Input to pipe. */
    TclFile errorFile;          /* Error output from pipe. */
    int numPids;                /* How many processes are attached to this
                                 * pipe? */
    Tcl_Pid *pidPtr;            /* The process IDs themselves. Allocated by
                                 * the creator of the pipe. */
    int isNonBlocking;          /* Nonzero when the pipe is in nonblocking
                                 * mode. Used to decide whether to wait for
                                 * the children at close time. */
} PipeState;

/*
 * Declarations for local functions defined in this file:
 */

static int              PipeBlockModeProc(ClientData instanceData, int mode);
static int              PipeCloseProc(ClientData instanceData,
                            Tcl_Interp *interp);
static int              PipeGetHandleProc(ClientData instanceData,
                            int direction, ClientData *handlePtr);
static int              PipeInputProc(ClientData instanceData, char *buf,
                            int toRead, int *errorCode);
static int              PipeOutputProc(ClientData instanceData,
                            const char *buf, int toWrite, int *errorCode);
static void             PipeWatchProc(ClientData instanceData, int mask);
static void             RestoreSignals(void);
static int              SetupStdFile(TclFile file, int type);

/*
 * This structure describes the channel type structure for command pipe based
 * I/O:
 */

static Tcl_ChannelType pipeChannelType = {
    "pipe",                     /* Type name. */
    TCL_CHANNEL_VERSION_5,      /* v5 channel */
    PipeCloseProc,              /* Close proc. */
    PipeInputProc,              /* Input proc. */
    PipeOutputProc,             /* Output proc. */
    NULL,                       /* Seek proc. */
    NULL,                       /* Set option proc. */
    NULL,                       /* Get option proc. */
    PipeWatchProc,              /* Initialize notifier. */
    PipeGetHandleProc,          /* Get OS handles out of channel. */
    NULL,                       /* close2proc. */
    PipeBlockModeProc,          /* Set blocking or non-blocking mode.*/
    NULL,                       /* flush proc. */
    NULL,                       /* handler proc. */
    NULL,                       /* wide seek proc */
    NULL,                       /* thread action proc */
    NULL,                       /* truncation */
};

/*
 *----------------------------------------------------------------------
 *
 * TclpMakeFile --
 *
 *      Make a TclFile from a channel.
 *
 * Results:
 *      Returns a new TclFile or NULL on failure.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclpMakeFile(
    Tcl_Channel channel,        /* Channel to get file from. */
    int direction)              /* Either TCL_READABLE or TCL_WRITABLE. */
{
    ClientData data;

    if (Tcl_GetChannelHandle(channel, direction,
            (ClientData *) &data) == TCL_OK) {
        return MakeFile(PTR2INT(data));
    } else {
        return (TclFile) NULL;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * TclpOpenFile --
 *
 *      Open a file for use in a pipeline.
 *
 * Results:
 *      Returns a new TclFile handle or NULL on failure.
 *
 * Side effects:
 *      May cause a file to be created on the file system.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclpOpenFile(
    const char *fname,          /* The name of the file to open. */
    int mode)                   /* In what mode to open the file? */
{
    int fd;
    const char *native;
    Tcl_DString ds;

    native = Tcl_UtfToExternalDString(NULL, fname, -1, &ds);
    fd = TclOSopen(native, mode, 0666);                 /* INTL: Native. */
    Tcl_DStringFree(&ds);
    if (fd != -1) {
        fcntl(fd, F_SETFD, FD_CLOEXEC);

        /*
         * If the file is being opened for writing, seek to the end so we can
         * append to any data already in the file.
         */

        if ((mode & O_WRONLY) && !(mode & O_APPEND)) {
            TclOSseek(fd, (Tcl_SeekOffset) 0, SEEK_END);
        }

        /*
         * Increment the fd so it can't be 0, which would conflict with the
         * NULL return for errors.
         */

        return MakeFile(fd);
    }
    return NULL;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreateTempFile --
 *
 *      This function creates a temporary file initialized with an optional
 *      string, and returns a file handle with the file pointer at the
 *      beginning of the file.
 *
 * Results:
 *      A handle to a file.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

TclFile
TclpCreateTempFile(
    const char *contents)       /* String to write into temp file, or NULL. */
{
    char fileName[L_tmpnam + 9];
    const char *native;
    Tcl_DString dstring;
    int fd;

    /*
     * We should also check against making more then TMP_MAX of these.
     */

    strcpy(fileName, P_tmpdir);                         /* INTL: Native. */
    if (fileName[strlen(fileName) - 1] != '/') {
        strcat(fileName, "/");                          /* INTL: Native. */
    }
    strcat(fileName, "tclXXXXXX");
    fd = mkstemp(fileName);                             /* INTL: Native. */
    if (fd == -1) {
        return NULL;
    }
    fcntl(fd, F_SETFD, FD_CLOEXEC);
    unlink(fileName);                                   /* INTL: Native. */

    if (contents != NULL) {
        native = Tcl_UtfToExternalDString(NULL, contents, -1, &dstring);
        if (write(fd, native, strlen(native)) == -1) {
            close(fd);
            Tcl_DStringFree(&dstring);
            return NULL;
        }
        Tcl_DStringFree(&dstring);
        TclOSseek(fd, (Tcl_SeekOffset) 0, SEEK_SET);
    }
    return MakeFile(fd);
}

/*
 *----------------------------------------------------------------------
 *
 * TclpTempFileName --
 *
 *      This function returns unique filename.
 *
 * Results:
 *      Returns a valid Tcl_Obj* with refCount 0, or NULL on failure.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

Tcl_Obj *
TclpTempFileName(void)
{
    char fileName[L_tmpnam + 9];
    Tcl_Obj *result = NULL;
    int fd;

    /*
     * We should also check against making more then TMP_MAX of these.
     */

    strcpy(fileName, P_tmpdir);         /* INTL: Native. */
    if (fileName[strlen(fileName) - 1] != '/') {
        strcat(fileName, "/");          /* INTL: Native. */
    }
    strcat(fileName, "tclXXXXXX");
    fd = mkstemp(fileName);             /* INTL: Native. */
    if (fd == -1) {
        return NULL;
    }
    fcntl(fd, F_SETFD, FD_CLOEXEC);
    unlink(fileName);                   /* INTL: Native. */

    result = TclpNativeToNormalized((ClientData) fileName);
    close(fd);
    return result;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreatePipe --
 *
 *      Creates a pipe - simply calls the pipe() function.
 *
 * Results:
 *      Returns 1 on success, 0 on failure.
 *
 * Side effects:
 *      Creates a pipe.
 *
 *----------------------------------------------------------------------
 */

int
TclpCreatePipe(
    TclFile *readPipe,          /* Location to store file handle for read side
                                 * of pipe. */
    TclFile *writePipe)         /* Location to store file handle for write
                                 * side of pipe. */
{
    int pipeIds[2];

    if (pipe(pipeIds) != 0) {
        return 0;
    }

    fcntl(pipeIds[0], F_SETFD, FD_CLOEXEC);
    fcntl(pipeIds[1], F_SETFD, FD_CLOEXEC);

    *readPipe = MakeFile(pipeIds[0]);
    *writePipe = MakeFile(pipeIds[1]);
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCloseFile --
 *
 *      Implements a mechanism to close a UNIX file.
 *
 * Results:
 *      Returns 0 on success, or -1 on error, setting errno.
 *
 * Side effects:
 *      The file is closed.
 *
 *----------------------------------------------------------------------
 */

int
TclpCloseFile(
    TclFile file)       /* The file to close. */
{
    int fd = GetFd(file);

    /*
     * Refuse to close the fds for stdin, stdout and stderr.
     */

    if ((fd == 0) || (fd == 1) || (fd == 2)) {
        return 0;
    }

    Tcl_DeleteFileHandler(fd);
    return close(fd);
}

/*
 *---------------------------------------------------------------------------
 *
 * TclpCreateProcess --
 *
 *      Create a child process that has the specified files as its standard
 *      input, output, and error. The child process runs asynchronously and
 *      runs with the same environment variables as the creating process.
 *
 *      The path is searched to find the specified executable.
 *
 * Results:
 *      The return value is TCL_ERROR and an error message is left in the
 *      interp's result if there was a problem creating the child process.
 *      Otherwise, the return value is TCL_OK and *pidPtr is filled with the
 *      process id of the child process.
 *
 * Side effects:
 *      A process is created.
 *
 *---------------------------------------------------------------------------
 */

    /* ARGSUSED */
int
TclpCreateProcess(
    Tcl_Interp *interp,         /* Interpreter in which to leave errors that
                                 * occurred when creating the child process.
                                 * Error messages from the child process
                                 * itself are sent to errorFile. */
    int argc,                   /* Number of arguments in following array. */
    const char **argv,          /* Array of argument strings in UTF-8.
                                 * argv[0] contains the name of the executable
                                 * translated using Tcl_TranslateFileName
                                 * call). Additional arguments have not been
                                 * converted. */
    TclFile inputFile,          /* If non-NULL, gives the file to use as input
                                 * for the child process. If inputFile file is
                                 * not readable or is NULL, the child will
                                 * receive no standard input. */
    TclFile outputFile,         /* If non-NULL, gives the file that receives
                                 * output from the child process. If
                                 * outputFile file is not writeable or is
                                 * NULL, output from the child will be
                                 * discarded. */
    TclFile errorFile,          /* If non-NULL, gives the file that receives
                                 * errors from the child process. If errorFile
                                 * file is not writeable or is NULL, errors
                                 * from the child will be discarded. errorFile
                                 * may be the same as outputFile. */
    Tcl_Pid *pidPtr)            /* If this function is successful, pidPtr is
                                 * filled with the process id of the child
                                 * process. */
{
    TclFile errPipeIn, errPipeOut;
    int count, status, fd;
    char errSpace[200 + TCL_INTEGER_SPACE];
    Tcl_DString *dsArray;
    char **newArgv;
    int pid, i;

    errPipeIn = NULL;
    errPipeOut = NULL;
    pid = -1;

    /*
     * Create a pipe that the child can use to return error information if
     * anything goes wrong.
     */

    if (TclpCreatePipe(&errPipeIn, &errPipeOut) == 0) {
        Tcl_AppendResult(interp, "couldn't create pipe: ",
                Tcl_PosixError(interp), NULL);
        goto error;
    }

    /*
     * We need to allocate and convert this before the fork so it is properly
     * deallocated later
     */

    dsArray = (Tcl_DString *)
            TclStackAlloc(interp, argc * sizeof(Tcl_DString));
    newArgv = (char **) TclStackAlloc(interp, (argc+1) * sizeof(char *));
    newArgv[argc] = NULL;
    for (i = 0; i < argc; i++) {
        newArgv[i] = Tcl_UtfToExternalDString(NULL, argv[i], -1, &dsArray[i]);
    }

#ifdef USE_VFORK
    /*
     * After vfork(), do not call code in the child that changes global state,
     * because it is using the parent's memory space at that point and writes
     * might corrupt the parent: so ensure standard channels are initialized in
     * the parent, otherwise SetupStdFile() might initialize them in the child.
     */
    if (!inputFile) {
        Tcl_GetStdChannel(TCL_STDIN);
    }
    if (!outputFile) {
        Tcl_GetStdChannel(TCL_STDOUT);
    }
    if (!errorFile) {
        Tcl_GetStdChannel(TCL_STDERR);
    }
#endif
    pid = fork();
    if (pid == 0) {
        int joinThisError = errorFile && (errorFile == outputFile);

        fd = GetFd(errPipeOut);

        /*
         * Set up stdio file handles for the child process.
         */

        if (!SetupStdFile(inputFile, TCL_STDIN)
                || !SetupStdFile(outputFile, TCL_STDOUT)
                || (!joinThisError && !SetupStdFile(errorFile, TCL_STDERR))
                || (joinThisError &&
                        ((dup2(1,2) == -1) || (fcntl(2, F_SETFD, 0) != 0)))) {
            sprintf(errSpace,
                    "%dforked process couldn't set up input/output: ", errno);
            (void)write(fd, errSpace, (size_t) strlen(errSpace));
            _exit(1);
        }

        /*
         * Close the input side of the error pipe.
         */

        RestoreSignals();
        execvp(newArgv[0], newArgv);                    /* INTL: Native. */
        sprintf(errSpace, "%dcouldn't execute \"%.150s\": ", errno, argv[0]);
        (void)write(fd, errSpace, (size_t) strlen(errSpace));
        _exit(1);
    }

    /*
     * Free the mem we used for the fork
     */

    for (i = 0; i < argc; i++) {
        Tcl_DStringFree(&dsArray[i]);
    }
    TclStackFree(interp, newArgv);
    TclStackFree(interp, dsArray);

    if (pid == -1) {
        Tcl_AppendResult(interp, "couldn't fork child process: ",
                Tcl_PosixError(interp), NULL);
        goto error;
    }

    /*
     * Read back from the error pipe to see if the child started up OK. The
     * info in the pipe (if any) consists of a decimal errno value followed by
     * an error message.
     */

    TclpCloseFile(errPipeOut);
    errPipeOut = NULL;

    fd = GetFd(errPipeIn);
    count = read(fd, errSpace, (size_t) (sizeof(errSpace) - 1));
    if (count > 0) {
        char *end;
        errSpace[count] = 0;
        errno = strtol(errSpace, &end, 10);
        Tcl_AppendResult(interp, end, Tcl_PosixError(interp), NULL);
        goto error;
    }

    TclpCloseFile(errPipeIn);
    *pidPtr = (Tcl_Pid) INT2PTR(pid);
    return TCL_OK;

  error:
    if (pid != -1) {
        /*
         * Reap the child process now if an error occurred during its startup.
         * We don't call this with WNOHANG because that can lead to defunct
         * processes on an MP system. We shouldn't have to worry about hanging
         * here, since this is the error case. [Bug: 6148]
         */

        Tcl_WaitPid((Tcl_Pid) INT2PTR(pid), &status, 0);
    }

    if (errPipeIn) {
        TclpCloseFile(errPipeIn);
    }
    if (errPipeOut) {
        TclpCloseFile(errPipeOut);
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * RestoreSignals --
 *
 *      This function is invoked in a forked child process just before
 *      exec-ing a new program to restore all signals to their default
 *      settings.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Signal settings get changed.
 *
 *----------------------------------------------------------------------
 */

static void
RestoreSignals(void)
{
#ifdef SIGABRT
    signal(SIGABRT, SIG_DFL);
#endif
#ifdef SIGALRM
    signal(SIGALRM, SIG_DFL);
#endif
#ifdef SIGFPE
    signal(SIGFPE, SIG_DFL);
#endif
#ifdef SIGHUP
    signal(SIGHUP, SIG_DFL);
#endif
#ifdef SIGILL
    signal(SIGILL, SIG_DFL);
#endif
#ifdef SIGINT
    signal(SIGINT, SIG_DFL);
#endif
#ifdef SIGPIPE
    signal(SIGPIPE, SIG_DFL);
#endif
#ifdef SIGQUIT
    signal(SIGQUIT, SIG_DFL);
#endif
#ifdef SIGSEGV
    signal(SIGSEGV, SIG_DFL);
#endif
#ifdef SIGTERM
    signal(SIGTERM, SIG_DFL);
#endif
#ifdef SIGUSR1
    signal(SIGUSR1, SIG_DFL);
#endif
#ifdef SIGUSR2
    signal(SIGUSR2, SIG_DFL);
#endif
#ifdef SIGCHLD
    signal(SIGCHLD, SIG_DFL);
#endif
#ifdef SIGCONT
    signal(SIGCONT, SIG_DFL);
#endif
#ifdef SIGTSTP
    signal(SIGTSTP, SIG_DFL);
#endif
#ifdef SIGTTIN
    signal(SIGTTIN, SIG_DFL);
#endif
#ifdef SIGTTOU
    signal(SIGTTOU, SIG_DFL);
#endif
}

/*
 *----------------------------------------------------------------------
 *
 * SetupStdFile --
 *
 *      Set up stdio file handles for the child process, using the current
 *      standard channels if no other files are specified. If no standard
 *      channel is defined, or if no file is associated with the channel, then
 *      the corresponding standard fd is closed.
 *
 * Results:
 *      Returns 1 on success, or 0 on failure.
 *
 * Side effects:
 *      Replaces stdio fds.
 *
 *----------------------------------------------------------------------
 */

static int
SetupStdFile(
    TclFile file,               /* File to dup, or NULL. */
    int type)                   /* One of TCL_STDIN, TCL_STDOUT, TCL_STDERR */
{
    Tcl_Channel channel;
    int fd;
    int targetFd = 0;           /* Initializations here needed only to */
    int direction = 0;          /* prevent warnings about using uninitialized
                                 * variables. */

    switch (type) {
    case TCL_STDIN:
        targetFd = 0;
        direction = TCL_READABLE;
        break;
    case TCL_STDOUT:
        targetFd = 1;
        direction = TCL_WRITABLE;
        break;
    case TCL_STDERR:
        targetFd = 2;
        direction = TCL_WRITABLE;
        break;
    }

    if (!file) {
        channel = Tcl_GetStdChannel(type);
        if (channel) {
            file = TclpMakeFile(channel, direction);
        }
    }
    if (file) {
        fd = GetFd(file);
        if (fd != targetFd) {
            if (dup2(fd, targetFd) == -1) {
                return 0;
            }

            /*
             * Must clear the close-on-exec flag for the target FD, since some
             * systems (e.g. Ultrix) do not clear the CLOEXEC flag on the
             * target FD.
             */

            fcntl(targetFd, F_SETFD, 0);
        } else {
            /*
             * Since we aren't dup'ing the file, we need to explicitly clear
             * the close-on-exec flag.
             */

            fcntl(fd, F_SETFD, 0);
        }
    } else {
        close(targetFd);
    }
    return 1;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpCreateCommandChannel --
 *
 *      This function is called by the generic IO level to perform the
 *      platform specific channel initialization for a command channel.
 *
 * Results:
 *      Returns a new channel or NULL on failure.
 *
 * Side effects:
 *      Allocates a new channel.
 *
 *----------------------------------------------------------------------
 */

Tcl_Channel
TclpCreateCommandChannel(
    TclFile readFile,           /* If non-null, gives the file for reading. */
    TclFile writeFile,          /* If non-null, gives the file for writing. */
    TclFile errorFile,          /* If non-null, gives the file where errors
                                 * can be read. */
    int numPids,                /* The number of pids in the pid array. */
    Tcl_Pid *pidPtr)            /* An array of process identifiers. Allocated
                                 * by the caller, freed when the channel is
                                 * closed or the processes are detached (in a
                                 * background exec). */
{
    char channelName[16 + TCL_INTEGER_SPACE];
    int channelId;
    PipeState *statePtr = (PipeState *) ckalloc((unsigned) sizeof(PipeState));
    int mode;

    statePtr->inFile = readFile;
    statePtr->outFile = writeFile;
    statePtr->errorFile = errorFile;
    statePtr->numPids = numPids;
    statePtr->pidPtr = pidPtr;
    statePtr->isNonBlocking = 0;

    mode = 0;
    if (readFile) {
        mode |= TCL_READABLE;
    }
    if (writeFile) {
        mode |= TCL_WRITABLE;
    }

    /*
     * Use one of the fds associated with the channel as the channel id.
     */

    if (readFile) {
        channelId = GetFd(readFile);
    } else if (writeFile) {
        channelId = GetFd(writeFile);
    } else if (errorFile) {
        channelId = GetFd(errorFile);
    } else {
        channelId = 0;
    }

    /*
     * For backward compatibility with previous versions of Tcl, we use
     * "file%d" as the base name for pipes even though it would be more
     * natural to use "pipe%d".
     */

    sprintf(channelName, "file%d", channelId);
    statePtr->channel = Tcl_CreateChannel(&pipeChannelType, channelName,
            (ClientData) statePtr, mode);
    return statePtr->channel;
}

/*
 *----------------------------------------------------------------------
 *
 * TclGetAndDetachPids --
 *
 *      This function is invoked in the generic implementation of a
 *      background "exec" (an exec when invoked with a terminating "&") to
 *      store a list of the PIDs for processes in a command pipeline in the
 *      interp's result and to detach the processes.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Modifies the interp's result. Detaches processes.
 *
 *----------------------------------------------------------------------
 */

void
TclGetAndDetachPids(
    Tcl_Interp *interp,         /* Interpreter to append the PIDs to. */
    Tcl_Channel chan)           /* Handle for the pipeline. */
{
    PipeState *pipePtr;
    const Tcl_ChannelType *chanTypePtr;
    int i;
    char buf[TCL_INTEGER_SPACE];

    /*
     * Punt if the channel is not a command channel.
     */

    chanTypePtr = Tcl_GetChannelType(chan);
    if (chanTypePtr != &pipeChannelType) {
        return;
    }

    pipePtr = (PipeState *) Tcl_GetChannelInstanceData(chan);
    for (i = 0; i < pipePtr->numPids; i++) {
        TclFormatInt(buf, (long) TclpGetPid(pipePtr->pidPtr[i]));
        Tcl_AppendElement(interp, buf);
        Tcl_DetachPids(1, &(pipePtr->pidPtr[i]));
    }
    if (pipePtr->numPids > 0) {
        ckfree((char *) pipePtr->pidPtr);
        pipePtr->numPids = 0;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeBlockModeProc --
 *
 *      Helper function to set blocking and nonblocking modes on a pipe based
 *      channel. Invoked by generic IO level code.
 *
 * Results:
 *      0 if successful, errno when failed.
 *
 * Side effects:
 *      Sets the device into blocking or non-blocking mode.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
static int
PipeBlockModeProc(
    ClientData instanceData,    /* Pipe state. */
    int mode)                   /* The mode to set. Can be one of
                                 * TCL_MODE_BLOCKING or
                                 * TCL_MODE_NONBLOCKING. */
{
    PipeState *psPtr = instanceData;

    if (psPtr->inFile) {
        if (TclUnixSetBlockingMode(GetFd(psPtr->inFile), mode) < 0) {
            return errno;
        }
    }
    if (psPtr->outFile) {
        if (TclUnixSetBlockingMode(GetFd(psPtr->outFile), mode) < 0) {
            return errno;
        }
    }

    psPtr->isNonBlocking = (mode == TCL_MODE_NONBLOCKING);

    return 0;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeCloseProc --
 *
 *      This function is invoked by the generic IO level to perform
 *      channel-type-specific cleanup when a command pipeline channel is
 *      closed.
 *
 * Results:
 *      0 on success, errno otherwise.
 *
 * Side effects:
 *      Closes the command pipeline channel.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
static int
PipeCloseProc(
    ClientData instanceData,    /* The pipe to close. */
    Tcl_Interp *interp)         /* For error reporting. */
{
    PipeState *pipePtr;
    Tcl_Channel errChan;
    int errorCode, result;

    errorCode = 0;
    result = 0;
    pipePtr = (PipeState *) instanceData;
    if (pipePtr->inFile) {
        if (TclpCloseFile(pipePtr->inFile) < 0) {
            errorCode = errno;
        }
    }
    if (pipePtr->outFile) {
        if ((TclpCloseFile(pipePtr->outFile) < 0) && (errorCode == 0)) {
            errorCode = errno;
        }
    }

    if (pipePtr->isNonBlocking || TclInExit()) {
        /*
         * If the channel is non-blocking or Tcl is being cleaned up, just
         * detach the children PIDs, reap them (important if we are in a
         * dynamic load module), and discard the errorFile.
         */

        Tcl_DetachPids(pipePtr->numPids, pipePtr->pidPtr);
        Tcl_ReapDetachedProcs();

        if (pipePtr->errorFile) {
            TclpCloseFile(pipePtr->errorFile);
        }
    } else {
        /*
         * Wrap the error file into a channel and give it to the cleanup
         * routine.
         */

        if (pipePtr->errorFile) {
            errChan = Tcl_MakeFileChannel(
                (ClientData) INT2PTR(GetFd(pipePtr->errorFile)), TCL_READABLE);
        } else {
            errChan = NULL;
        }
        result = TclCleanupChildren(interp, pipePtr->numPids, pipePtr->pidPtr,
                errChan);
    }

    if (pipePtr->numPids != 0) {
        ckfree((char *) pipePtr->pidPtr);
    }
    ckfree((char *) pipePtr);
    if (errorCode == 0) {
        return result;
    }
    return errorCode;
}

/*
 *----------------------------------------------------------------------
 *
 * PipeInputProc --
 *
 *      This function is invoked from the generic IO level to read input from
 *      a command pipeline based channel.
 *
 * Results:
 *      The number of bytes read is returned or -1 on error. An output
 *      argument contains a POSIX error code if an error occurs, or zero.
 *
 * Side effects:
 *      Reads input from the input device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
PipeInputProc(
    ClientData instanceData,    /* Pipe state. */
    char *buf,                  /* Where to store data read. */
    int toRead,                 /* How much space is available in the
                                 * buffer? */
    int *errorCodePtr)          /* Where to store error code. */
{
    PipeState *psPtr = (PipeState *) instanceData;
    int bytesRead;              /* How many bytes were actually read from the
                                 * input device? */

    *errorCodePtr = 0;

    /*
     * Assume there is always enough input available. This will block
     * appropriately, and read will unblock as soon as a short read is
     * possible, if the channel is in blocking mode. If the channel is
     * nonblocking, the read will never block. Some OSes can throw an
     * interrupt error, for which we should immediately retry. [Bug #415131]
     */

    do {
        bytesRead = read(GetFd(psPtr->inFile), buf, (size_t) toRead);
    } while ((bytesRead < 0) && (errno == EINTR));

    if (bytesRead < 0) {
        *errorCodePtr = errno;
        return -1;
    } else {
        return bytesRead;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeOutputProc--
 *
 *      This function is invoked from the generic IO level to write output to
 *      a command pipeline based channel.
 *
 * Results:
 *      The number of bytes written is returned or -1 on error. An output
 *      argument contains a POSIX error code if an error occurred, or zero.
 *
 * Side effects:
 *      Writes output on the output device of the channel.
 *
 *----------------------------------------------------------------------
 */

static int
PipeOutputProc(
    ClientData instanceData,    /* Pipe state. */
    const char *buf,            /* The data buffer. */
    int toWrite,                /* How many bytes to write? */
    int *errorCodePtr)          /* Where to store error code. */
{
    PipeState *psPtr = (PipeState *) instanceData;
    int written;

    *errorCodePtr = 0;

    /*
     * Some OSes can throw an interrupt error, for which we should immediately
     * retry. [Bug #415131]
     */

    do {
        written = write(GetFd(psPtr->outFile), buf, (size_t) toWrite);
    } while ((written < 0) && (errno == EINTR));

    if (written < 0) {
        *errorCodePtr = errno;
        return -1;
    } else {
        return written;
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeWatchProc --
 *
 *      Initialize the notifier to watch the fds from this channel.
 *
 * Results:
 *      None.
 *
 * Side effects:
 *      Sets up the notifier so that a future event on the channel will be
 *      seen by Tcl.
 *
 *----------------------------------------------------------------------
 */

static void
PipeWatchProc(
    ClientData instanceData,    /* The pipe state. */
    int mask)                   /* Events of interest; an OR-ed combination of
                                 * TCL_READABLE, TCL_WRITABLE and
                                 * TCL_EXCEPTION. */
{
    PipeState *psPtr = (PipeState *) instanceData;
    int newmask;

    if (psPtr->inFile) {
        newmask = mask & (TCL_READABLE | TCL_EXCEPTION);
        if (newmask) {
            Tcl_CreateFileHandler(GetFd(psPtr->inFile), mask,
                    (Tcl_FileProc *) Tcl_NotifyChannel,
                    (ClientData) psPtr->channel);
        } else {
            Tcl_DeleteFileHandler(GetFd(psPtr->inFile));
        }
    }
    if (psPtr->outFile) {
        newmask = mask & (TCL_WRITABLE | TCL_EXCEPTION);
        if (newmask) {
            Tcl_CreateFileHandler(GetFd(psPtr->outFile), mask,
                    (Tcl_FileProc *) Tcl_NotifyChannel,
                    (ClientData) psPtr->channel);
        } else {
            Tcl_DeleteFileHandler(GetFd(psPtr->outFile));
        }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * PipeGetHandleProc --
 *
 *      Called from Tcl_GetChannelHandle to retrieve OS handles from inside a
 *      command pipeline based channel.
 *
 * Results:
 *      Returns TCL_OK with the fd in handlePtr, or TCL_ERROR if there is no
 *      handle for the specified direction.
 *
 * Side effects:
 *      None.
 *
 *----------------------------------------------------------------------
 */

static int
PipeGetHandleProc(
    ClientData instanceData,    /* The pipe state. */
    int direction,              /* TCL_READABLE or TCL_WRITABLE */
    ClientData *handlePtr)      /* Where to store the handle. */
{
    PipeState *psPtr = (PipeState *) instanceData;

    if (direction == TCL_READABLE && psPtr->inFile) {
        *handlePtr = (ClientData) INT2PTR(GetFd(psPtr->inFile));
        return TCL_OK;
    }
    if (direction == TCL_WRITABLE && psPtr->outFile) {
        *handlePtr = (ClientData) INT2PTR(GetFd(psPtr->outFile));
        return TCL_OK;
    }
    return TCL_ERROR;
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_WaitPid --
 *
 *      Implements the waitpid system call on Unix systems.
 *
 * Results:
 *      Result of calling waitpid.
 *
 * Side effects:
 *      Waits for a process to terminate.
 *
 *----------------------------------------------------------------------
 */

Tcl_Pid
Tcl_WaitPid(
    Tcl_Pid pid,
    int *statPtr,
    int options)
{
    int result;
    pid_t real_pid;

    real_pid = (pid_t) PTR2INT(pid);
    while (1) {
        result = (int) waitpid(real_pid, statPtr, options);
        if ((result != -1) || (errno != EINTR)) {
            return (Tcl_Pid) INT2PTR(result);
        }
    }
}

/*
 *----------------------------------------------------------------------
 *
 * Tcl_PidObjCmd --
 *
 *      This function is invoked to process the "pid" Tcl command. See the
 *      user documentation for details on what it does.
 *
 * Results:
 *      A standard Tcl result.
 *
 * Side effects:
 *      See the user documentation.
 *
 *----------------------------------------------------------------------
 */

        /* ARGSUSED */
int
Tcl_PidObjCmd(
    ClientData dummy,           /* Not used. */
    Tcl_Interp *interp,         /* Current interpreter. */
    int objc,                   /* Number of arguments. */
    Tcl_Obj *const *objv)       /* Argument strings. */
{
    if (objc > 2) {
        Tcl_WrongNumArgs(interp, 1, objv, "?channelId?");
        return TCL_ERROR;
    }
    if (objc == 1) {
        Tcl_SetObjResult(interp, Tcl_NewLongObj((long) getpid()));
    } else {
        Tcl_Channel chan;
        const Tcl_ChannelType *chanTypePtr;
        PipeState *pipePtr;
        int i;
        Tcl_Obj *resultPtr, *longObjPtr;

        chan = Tcl_GetChannel(interp, Tcl_GetString(objv[1]), NULL);
        if (chan == (Tcl_Channel) NULL) {
            return TCL_ERROR;
        }
        chanTypePtr = Tcl_GetChannelType(chan);
        if (chanTypePtr != &pipeChannelType) {
            return TCL_OK;
        }
        pipePtr = (PipeState *) Tcl_GetChannelInstanceData(chan);
        resultPtr = Tcl_NewObj();
        for (i = 0; i < pipePtr->numPids; i++) {
            longObjPtr = Tcl_NewLongObj((long) TclpGetPid(pipePtr->pidPtr[i]));
            Tcl_ListObjAppendElement(NULL, resultPtr, longObjPtr);
        }
        Tcl_SetObjResult(interp, resultPtr);
    }
    return TCL_OK;
}

/*
 *----------------------------------------------------------------------
 *
 * TclpFinalizePipes --
 *
 *      Cleans up the pipe subsystem from Tcl_FinalizeThread
 *
 * Results:
 *      None.
 *
 * Notes:
 *      This function carries out no operation on Unix.
 *
 *----------------------------------------------------------------------
 */

void
TclpFinalizePipes(void)
{
}

/*
 * Local Variables:
 * mode: c
 * c-basic-offset: 4
 * fill-column: 78
 * End:
 */