diff options
Diffstat (limited to 'doc/chan.n')
| -rw-r--r-- | doc/chan.n | 44 |
1 files changed, 41 insertions, 3 deletions
@@ -814,7 +814,44 @@ set data [chan read $f $numDataBytes] close $f .CE - +.SS "FILE SEEK EXAMPLES" +.PP +Read a file twice: +.PP +.CS +set f [open file.txt] +set data1 [chan read $f] +\fBchan seek\fR $f 0 +set data2 [chan read $f] +chan close $f +# $data1 eq $data2 if the file wasn't updated +.CE +.PP +Read the last 10 bytes from a file: +.PP +.CS +set f [open file.data] +# This is guaranteed to work with binary data but +# may fail with other encodings... +chan configure $f -translation binary +\fBchan seek\fR $f -10 end +set data [chan read $f 10] +chan close $f +.CE +.PP +Read a line from a file channel only if it starts with \fBfoobar\fR: +.PP +.CS +# Save the offset in case we need to undo the read... +set offset [\fBtell\fR $chan] +if {[read $chan 6] eq "foobar"} { + gets $chan line +} else { + set line {} + # Undo the read... + seek $chan $offset +} +.CE .SS "ENCODING ERROR EXAMPLES" .PP The example below illustrates handling of an encoding error encountered @@ -980,10 +1017,11 @@ vwait done .SH "SEE ALSO" close(n), eof(n), fblocked(n), fconfigure(n), fcopy(n), file(n), fileevent(n), flush(n), gets(n), open(n), puts(n), read(n), seek(n), -socket(n), tell(n), refchan(n), transchan(n) +socket(n), tell(n), refchan(n), transchan(n), +Tcl_StandardChannels(3) .SH KEYWORDS blocking, channel, end of file, events, input, non-blocking, -offset, output, readable, writable +offset, output, readable, seek, stdio, tell, writable '\" Local Variables: '\" mode: nroff '\" End: |