diff options
Diffstat (limited to 'doc/open.n')
| -rw-r--r-- | doc/open.n | 85 |
1 files changed, 61 insertions, 24 deletions
@@ -34,73 +34,84 @@ The \fIaccess\fR argument, if present, indicates the way in which the file In the first form \fIaccess\fR may have any of the following values: .TP 15 \fBr\fR +. Open the file for reading only; the file must already exist. This is the default value if \fIaccess\fR is not specified. .TP 15 \fBr+\fR +. Open the file for both reading and writing; the file must already exist. .TP 15 \fBw\fR +. Open the file for writing only. Truncate it if it exists. If it does not exist, create a new file. .TP 15 \fBw+\fR +. Open the file for reading and writing. Truncate it if it exists. If it does not exist, create a new file. .TP 15 \fBa\fR +. Open the file for writing only. If the file does not exist, create a new empty file. Set the file pointer to the end of the file prior to each write. .TP 15 \fBa+\fR +. Open the file for reading and writing. If the file does not exist, create a new empty file. Set the initial access position to the end of the file. -.VS 8.5 .PP All of the legal \fIaccess\fR values above may have the character \fBb\fR added as the second or third character in the value to -indicate that the opened channel should be configured with the -\fB\-translation binary\fR option, making the channel suitable for +indicate that the opened channel should be configured as if with the +\fBfconfigure\fR \fB\-translation binary\fR option, making the channel suitable for reading or writing of binary data. -.VE 8.5 .PP In the second form, \fIaccess\fR consists of a list of any of the following flags, all of which have the standard POSIX meanings. One of the flags must be either \fBRDONLY\fR, \fBWRONLY\fR or \fBRDWR\fR. .TP 15 \fBRDONLY\fR +. Open the file for reading only. .TP 15 \fBWRONLY\fR +. Open the file for writing only. .TP 15 \fBRDWR\fR +. Open the file for both reading and writing. .TP 15 \fBAPPEND\fR +. Set the file pointer to the end of the file prior to each write. -.VS 8.5 .TP 15 \fBBINARY\fR +. Configure the opened channel with the \fB\-translation binary\fR option. -.VE 8.5 .TP 15 \fBCREAT\fR +. Create the file if it does not already exist (without this flag it is an error for the file not to exist). .TP 15 \fBEXCL\fR +. If \fBCREAT\fR is also specified, an error is returned if the file already exists. .TP 15 \fBNOCTTY\fR +. If the file is a terminal device, this flag prevents the file from becoming the controlling terminal of the process. .TP 15 \fBNONBLOCK\fR +. Prevents the process from blocking while opening the file, and possibly in subsequent I/O operations. The exact behavior of this flag is system- and device-dependent; its use is discouraged @@ -110,6 +121,7 @@ For details refer to your system documentation on the \fBopen\fR system call's \fBO_NONBLOCK\fR flag. .TP 15 \fBTRUNC\fR +. If the file exists it is truncated to zero length. .PP If a new file is created as part of opening it, \fIpermissions\fR @@ -119,7 +131,7 @@ conjunction with the process's file mode creation mask. .SH "COMMAND PIPELINES" .PP If the first character of \fIfileName\fR is -.QW | +.QW \fB|\fR then the remaining characters of \fIfileName\fR are treated as a list of arguments that describe a command pipeline to invoke, in the same style as the @@ -127,10 +139,12 @@ arguments for \fBexec\fR. In this case, the channel identifier returned by \fBopen\fR may be used to write to the command's input pipe or read from its output pipe, depending on the value of \fIaccess\fR. -If write-only access is used (e.g. \fIaccess\fR is \fBw\fR), then -standard output for the pipeline is directed to the current standard +If write-only access is used (e.g. \fIaccess\fR is +.QW \fBw\fR ), +then standard output for the pipeline is directed to the current standard output unless overridden by the command. -If read-only access is used (e.g. \fIaccess\fR is \fBr\fR), +If read-only access is used (e.g. \fIaccess\fR is +.QW \fBr\fR ), standard input for the pipeline is taken from the current standard input unless overridden by the command. The id of the spawned process is accessible through the \fBpid\fR @@ -156,6 +170,7 @@ The \fBfconfigure\fR command can be used to query and set additional configuration options specific to serial ports (where supported): .TP \fB\-mode\fR \fIbaud\fB,\fIparity\fB,\fIdata\fB,\fIstop\fR +. This option is a set of 4 comma-separated values: the baud rate, parity, number of data bits, and number of stop bits for this serial port. The \fIbaud\fR rate is a simple integer that specifies the connection speed. @@ -172,6 +187,7 @@ data bits and should be an integer from 5 to 8, while \fIstop\fR is the number of stop bits and should be the integer 1 or 2. .TP \fB\-handshake\fR \fItype\fR +. (Windows and Unix). This option is used to setup automatic handshake control. Note that not all handshake types maybe supported by your operating system. The \fItype\fR parameter is case-independent. @@ -189,11 +205,13 @@ The \fB\-handshake\fR option cannot be queried. .RE .TP \fB\-queue\fR +. (Windows and Unix). The \fB\-queue\fR option can only be queried. It returns a list of two integers representing the current number of bytes in the input and output queue respectively. .TP \fB\-timeout\fR \fImsec\fR +. (Windows and Unix). This option is used to set the timeout for blocking read operations. It specifies the maximum interval between the reception of two bytes in milliseconds. @@ -203,6 +221,7 @@ nonblocking reads. This option cannot be queried. .TP \fB\-ttycontrol\fR \fI{signal boolean signal boolean ...}\fR +. (Windows and Unix). This option is used to setup the handshake output lines (see below) permanently or to send a BREAK over the serial line. The \fIsignal\fR names are case-independent. @@ -215,6 +234,7 @@ The result is unpredictable. The \fB\-ttycontrol\fR option cannot be queried. .TP \fB\-ttystatus\fR +. (Windows and Unix). The \fB\-ttystatus\fR option can only be queried. It returns the current modem status and handshake input signals (see below). @@ -223,12 +243,14 @@ e.g. \fB{CTS 1 DSR 0 RING 1 DCD 0}\fR. The \fIsignal\fR names are returned upper case. .TP \fB\-xchar\fR \fI{xonChar xoffChar}\fR +. (Windows and Unix). This option is used to query or change the software handshake characters. Normally the operating system default should be DC1 (0x11) and DC3 (0x13) representing the ASCII standard XON and XOFF characters. .TP \fB\-pollinterval\fR \fImsec\fR +. (Windows only). This option is used to set the maximum time between polling for fileevents. This affects the time interval between checking for events throughout the Tcl @@ -239,6 +261,7 @@ you want to poll the serial port more or less often than 10 msec \fB\-sysbuffer\fR \fIinSize\fR .TP \fB\-sysbuffer\fR \fI{inSize outSize}\fR +. (Windows only). This option is used to change the size of Windows system buffers for a serial channel. Especially at higher communication rates the default input buffer size of 4096 bytes can overrun @@ -246,10 +269,11 @@ for latent systems. The first form specifies the input buffer size, in the second form both input and output buffers are defined. .TP \fB\-lasterror\fR +. (Windows only). This option is query only. In case of a serial communication error, \fBread\fR or \fBputs\fR returns a general Tcl file I/O error. -\fBfconfigure -lasterror\fR can be called to get a list of error details. +\fBfconfigure\fR \fB\-lasterror\fR can be called to get a list of error details. See below for an explanation of the various error codes. .SH "SERIAL PORT SIGNALS" .PP @@ -261,29 +285,29 @@ lines and handshaking. Here we are using the terms \fIworkstation\fR for your computer and \fImodem\fR for the external device, because some signal names (DCD, RI) come from modems. Of course your external device may use these signal lines for other purposes. -.IP \fBTXD(output)\fR +.IP \fBTXD\fR(output) \fBTransmitted Data:\fR Outgoing serial data. -.IP \fBRXD(input)\fR +.IP \fBRXD\fR(input) \fBReceived Data:\fRIncoming serial data. -.IP \fBRTS(output)\fR +.IP \fBRTS\fR(output) \fBRequest To Send:\fR This hardware handshake line informs the modem that your workstation is ready to receive data. Your workstation may automatically reset this signal to indicate that the input buffer is full. -.IP \fBCTS(input)\fR +.IP \fBCTS\fR(input) \fBClear To Send:\fR The complement to RTS. Indicates that the modem is ready to receive data. -.IP \fBDTR(output)\fR +.IP \fBDTR\fR(output) \fBData Terminal Ready:\fR This signal tells the modem that the workstation is ready to establish a link. DTR is often enabled automatically whenever a serial port is opened. -.IP \fBDSR(input)\fR +.IP \fBDSR\fR(input) \fBData Set Ready:\fR The complement to DTR. Tells the workstation that the modem is ready to establish a link. -.IP \fBDCD(input)\fR +.IP \fBDCD\fR(input) \fBData Carrier Detect:\fR This line becomes active when a modem detects a .QW Carrier signal. -.IP \fBRI(input)\fR +.IP \fBRI\fR(input) \fBRing Indicator:\fR Goes active when the modem detects an incoming call. .IP \fBBREAK\fR A BREAK condition is not a hardware signal line, but a logical zero on the @@ -299,39 +323,46 @@ event polling in background. The external device may have been switched off, the data lines may be noisy, system buffers may overrun or your mode settings may be wrong. That is why a reliable software should always \fBcatch\fR serial read operations. In cases of an error Tcl returns a -general file I/O error. Then \fBfconfigure -lasterror\fR may help to +general file I/O error. Then \fBfconfigure\fR \fB\-lasterror\fR may help to locate the problem. The following error codes may be returned. .TP 10 \fBRXOVER\fR +. Windows input buffer overrun. The data comes faster than your scripts reads -it or your system is overloaded. Use \fBfconfigure -sysbuffer\fR to avoid a +it or your system is overloaded. Use \fBfconfigure\fR \fB\-sysbuffer\fR to avoid a temporary bottleneck and/or make your script faster. .TP 10 \fBTXFULL\fR +. Windows output buffer overrun. Complement to RXOVER. This error should practically not happen, because Tcl cares about the output buffer status. .TP 10 \fBOVERRUN\fR +. UART buffer overrun (hardware) with data lost. The data comes faster than the system driver receives it. Check your advanced serial port settings to enable the FIFO (16550) buffer and/or setup a lower(1) interrupt threshold value. .TP 10 \fBRXPARITY\fR +. A parity error has been detected by your UART. -Wrong parity settings with \fBfconfigure -mode\fR or a noisy data line (RXD) +Wrong parity settings with \fBfconfigure\fR \fB\-mode\fR or a noisy data line (RXD) may cause this error. .TP 10 \fBFRAME\fR +. A stop-bit error has been detected by your UART. -Wrong mode settings with \fBfconfigure -mode\fR or a noisy data line (RXD) +Wrong mode settings with \fBfconfigure\fR \fB\-mode\fR or a noisy data line (RXD) may cause this error. .TP 10 \fBBREAK\fR +. A BREAK condition has been detected by your UART (see above). .SH "PORTABILITY ISSUES" .TP \fBWindows \fR +. Valid values for \fIfileName\fR to open a serial port are of the form \fBcom\fIX\fB\fR, where \fIX\fR is a number, generally from 1 to 9. A legacy form accepted as well is \fBcom\fIX\fB:\fR. This notation only @@ -339,8 +370,8 @@ works for serial ports from 1 to 9. An attempt to open a serial port that does not exist or has a number greater than 9 will fail. An alternate form of opening serial ports is to use the filename \fB//./comX\fR, where X is any number that corresponds to a serial port. -.RS .PP +.RS When running Tcl interactively, there may be some strange interactions between the real console, if one is present, and a command pipeline that uses standard input or output. If a command pipeline is opened for reading, some @@ -355,6 +386,7 @@ redirected from or to a file, then the above problems do not occur. .RE .TP \fBUnix\fR\0\0\0\0\0\0\0 +. Valid values for \fIfileName\fR to open a serial port are generally of the form \fB/dev/tty\fIX\fR, where \fIX\fR is \fBa\fR or \fBb\fR, but the name of any pseudo-file that maps to a serial port may be used. @@ -377,7 +409,9 @@ See the \fBPORTABILITY ISSUES\fR section of the \fBexec\fR command for additional information not specific to command pipelines about executing applications on the various platforms .SH "EXAMPLE" +.PP Open a command pipeline and catch any errors: +.PP .CS set fl [\fBopen\fR "| ls this_file_does_not_exist"] set data [read $fl] @@ -391,3 +425,6 @@ puts(n), exec(n), pid(n), fopen(3) .SH KEYWORDS access mode, append, create, file, non-blocking, open, permissions, pipeline, process, serial +'\"Local Variables: +'\"mode: nroff +'\"End: |