Open System Services Library Calls Reference Manual (G06.29+, H06.08+, J06.03+)

OSS Library Calls (e - f) edfseek(3)
Relative positioning (using pos_base values SEEK_CUR or SEEK_END) is slower than abso-
lute positioning (using pos_base value SEEK_SET) because it requires sequential scanning of
the file.
For absolute positioning (using pos_base value SEEK_SET), pos is the Edit line number multi-
plied by 1000. For example, 23000L corresponds to line 23, and 44120L corresponds to line
44.12.
Using absolute positioning, edfseek( ) sets the file position to the specified line if and only if the
specified line exists in the file. If the specified line does not exist in the file, edfseek( ) sets the file
position to the lowest-numbered line whose number exceeds the specified line number. If no
such line exists, edfseek( ) sets the file position past the end-of-file by selecting the line number
that a subsequent write operation would generate.
For example, assume that a file contains lines 1000, 1500, 2000, 2100. Specifying edfseek(...,
SEEK_SET):
• for lines 0..999 sets the position to line 1000.
• for lines 1001..1499 sets the position to line 1500.
• for line 1500 sets the position to line 1500.
• for line 2100 sets the position to line 2100.
• for lines 2101 and beyond sets the position to line 3000.
If an Edit file is empty, edfseek(... , SEEK_SET) for any specified line sets the file position to
line 1000.
The purpose of edfseek( ) with the SEEK_SET option is to set the file’s current position to a line
that is known to exist: for example, at a line with a location captured by a prior call to edftell( ).
edfseek(... , SEEK_SET) will not adjust the file position to an arbitrary nonexistent line that the
program intends to generate with a subsequent write. So, if a file contains lines 1000 and 2000,
you cannot use edfseek(fp, 1500, SEEK_SET) to cause fprintf(fp, ... ) to generate a new line
numbered 1500.
RETURN VALUES
Upon successful completion, the value 0 (zero) is returned. Otherwise, edfseek( ) returns EOF
and sets errno.
ERRORS
If the following condition occurs, the edfseek( ) function sets errno to the corresponding value:
[EINVAL] The stream is an invalid stream.
For all other error conditions, errno is set to the Guardian file-system error number. Refer to the
Guardian Procedure Errors and Messages Manual for more information about a specific Guar-
dian file-system error.
RELATED INFORMATION
Functions: edftell(3).
STANDARDS CONFORMANCE
The edfseek( ) function is an HP extension to the XPG4 Version 2 specification.
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