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.help zsektx May84 "System Interface"
.ih
NAME
zsektx -- seek on a text file
.ih
SYNOPSIS
.nf
zsektx (chan, loffset, status)
int chan # OS channel of text file
long loffset # magic seek offset
int status
.fi
.ih
DESCRIPTION
Text files are normally accessed sequentially, but random access is possible
when reading if \fBzsektx\fR is used to adjust the file position.
The primitive \fBzsektx\fR may be used to set the file position to BOF, EOF,
or to the beginning of any line in the file provided the offset of the line
was determined in a prior call to \fBznottx\fR while reading or writing the
file.
.ih
RETURN VALUE
ERR is returned if there is something wrong with \fIchan\fR or if seeks are
illegal on the device and the seek is to a file position other than BOF or
EOF. If seeks are illegal on the device a request to seek to BOF or EOF is
ignored. OK is returned if the seek is successful.
.ih
NOTES
Depending on the host system, \fIloffset\fR might be a zero indexed byte
offset, the logical record number, the file block number and char offset
within the block packed into a long integer, or some other machine dependent
quantity. The high level code must do nothing with \fIloffset\fR but
request it with \fBznottx\fR and pass the value on to \fBzsektx\fR to perform
a seek. The only way to generate a seek offset for a text file (other than
to BOF or EOF) is to note the file position while reading or writing the file.
A note followed by a seek while reading or writing a line (newline not yet
seen) rewinds the line.
.ih
SEE ALSO
znottx, zfiotx
.endhelp
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