diff options
Diffstat (limited to 'doc/read.n')
| -rw-r--r-- | doc/read.n | 73 |
1 files changed, 52 insertions, 21 deletions
@@ -5,10 +5,8 @@ '\" See the file "license.terms" for information on usage and redistribution '\" of this file, and for a DISCLAIMER OF ALL WARRANTIES. '\" -'\" RCS: @(#) $Id: read.n,v 1.4 1999/05/05 01:19:42 stanton Exp $ -'\" -.so man.macros .TH read n 8.1 Tcl "Tcl Built-In Commands" +.so man.macros .BS '\" Note: do not modify the .SH NAME line immediately below! .SH NAME @@ -18,20 +16,24 @@ read \- Read from a channel .sp \fBread \fIchannelId numChars\fR .BE - .SH DESCRIPTION .PP In the first form, the \fBread\fR command reads all of the data from -\fIchannelId\fR up to the end of the file. -If the \fB\-nonewline\fR switch is specified then the last character -of the file is discarded if it is a newline. -.VS 8.1 -In the second form, the extra argument specifies how many characters to -read. Exactly that many characters will be read and returned, unless -there are fewer than \fInumChars\fR left in the file; in this case -all the remaining characters are returned. If the channel is -configured to use a multi-byte encoding, then the number of characters -read may not be the same as the number of bytes read. +\fIchannelId\fR up to the end of the file. If the \fB\-nonewline\fR +switch is specified then the last character of the file is discarded +if it is a newline. In the second form, the extra argument specifies +how many characters to read. Exactly that many characters will be +read and returned, unless there are fewer than \fInumChars\fR left in +the file; in this case all the remaining characters are returned. If +the channel is configured to use a multi-byte encoding, then the +number of characters read may not be the same as the number of bytes +read. +.PP +\fIChannelId\fR must be an identifier for an open channel such as the +Tcl standard input channel (\fBstdin\fR), the return value from an +invocation of \fBopen\fR or \fBsocket\fR, or the result of a channel +creation command provided by a Tcl extension. The channel must have +been opened for input. .PP If \fIchannelId\fR is in nonblocking mode, the command may not read as many characters as requested: once all available input has been read, @@ -40,19 +42,48 @@ blocking for more input. If the channel is configured to use a multi-byte encoding, then there may actually be some bytes remaining in the internal buffers that do not form a complete character. These bytes will not be returned until a complete character is available or -end-of-file is reached. -.VE 8.1 -The \fB\-nonewline\fR switch is ignored if the command returns -before reaching the end of the file. +end-of-file is reached. The \fB\-nonewline\fR switch is ignored if +the command returns before reaching the end of the file. .PP \fBRead\fR translates end-of-line sequences in the input into newline characters according to the \fB\-translation\fR option for the channel. See the \fBfconfigure\fR manual entry for a discussion on ways in which \fBfconfigure\fR will alter input. - +.SH "USE WITH SERIAL PORTS" +'\" Note: this advice actually applies to many versions of Tcl +.PP +For most applications a channel connected to a serial port should be +configured to be nonblocking: \fBfconfigure\fI channelId \fB\-blocking +\fI0\fR. Then \fBread\fR behaves much like described above. Care +must be taken when using \fBread\fR on blocking serial ports: +.TP +\fBread \fIchannelId numChars\fR +. +In this form \fBread\fR blocks until \fInumChars\fR have been received +from the serial port. +.TP +\fBread \fIchannelId\fR +. +In this form \fBread\fR blocks until the reception of the end-of-file +character, see \fBfconfigure\fR \fB\-eofchar\fR. If there no end-of-file +character has been configured for the channel, then \fBread\fR will +block forever. +.SH "EXAMPLE" +.PP +This example code reads a file all at once, and splits it into a list, +with each line in the file corresponding to an element in the list: +.PP +.CS +set fl [open /proc/meminfo] +set data [\fBread\fR $fl] +close $fl +set lines [split $data \en] +.CE .SH "SEE ALSO" -eof(n), fblocked(n), fconfigure(n) - +file(n), eof(n), fblocked(n), fconfigure(n), Tcl_StandardChannels(3) .SH KEYWORDS blocking, channel, end of line, end of file, nonblocking, read, translation, encoding +'\"Local Variables: +'\"mode: nroff +'\"End: |