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.help znottx May84 "System Interface"
.ih
NAME
znottx -- note position in text file for a later seek
.ih
SYNOPSIS
.nf
znottx (chan, loffset)
int chan # OS channel of text file
long loffset # magic seek offset
.fi
.ih
DESCRIPTION
The absolute seek offset of the "current line" is returned in the long integer
variable \fIloffset\fR. If the file is opened for reading the offset
of the line which was just read or which is currently being read is returned.
If the file is opened for writing the offset of the next line to be written
or of the line currently being written is returned. In all cases the
offset points to the first character in a line, i.e., the first character
following the newline line delimiter character.
.ih
RETURN VALUE
If the operation is successful a magic integer describing the current file
offset is returned in \fIloffset\fR. If seeking is illegal on the device
associated with \fIchan\fR the return value is undefined. It is not an error
to call \fIznottx\fR on a file which does not permit seeks; if no seek is
ever performed no error has occurred.
.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. Seek offsets may be compared for equality but no other arithmetic
or logical operations are permissible. For example, if the offset of line A
is numerically less than the offset of line B, one \fIcannot\fR conclude that
line A is nearer the beginning of file than line B.
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.
.ih
SEE ALSO
zsektx, zfiotx
.endhelp
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