.help imokwl,imgnkw,imckwl Sep86 imfort
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NAME
.nf
imokwl -- open an image header keyword list
imgnkw -- get the next keyword from the list
imckwl -- close the keyword list
.fi
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SYNOPSIS
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subroutine imokwl (im, patstr, sortit, kwl, ier)

integer		im		#I image descriptor of open image
character*(*)	patstr		#I pattern matching subset of keywords
logical		sortit		#I sort the list by keyword name?
integer		kwl		#O keyword list descriptor
integer		ier		#O status return

subroutine imgnkw (kwl, outstr, ier)

integer		kwl		#I keyword list descriptor
character*(*)	outstr		#O the next keyword name
integer		ier		#O status return

subroutine imckwl (kwl, ier)

integer		kwl		#I keyword list descriptor
integer		ier		#O status return
.fi
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DESCRIPTION
The keyword list package is used to define some subset of the keywords in an
image header, and then read successive elements of the set, i.e., read back
the keyword names.  The keyword names are normally used as input to
\fIimtypk\fR or one of the \fIimgkw\fR procedures to obtain additional
information about each keyword.  The keyword list package is the only means
whereby a program can examine the contents of an image header without knowing
in advance the names of the individual header keywords.  A typical application
of the keyword list package is listing the contents of an image header.

The pattern string \fIpatstr\fR is used to specify the subset of header keywords
to be used to form the output list.  Some useful values are "*", which returns
the names of all header keywords, and "i_", which returns the names of only the
standard header keywords.  If the pattern string does not contain any pattern
matching meta-characters it is treated as a prefix string (e.g., as "^patstr*").
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RETURN VALUE
The \fIimokwl\fR procedure returns a nonzero status only if it runs out of
storage for the keyword list.  It is not an error for a list to be empty.
The \fIimgnkw\fR procedure returns a nonzero status when the end of the
keyword list is reached.

.nf
SYS_IMFNOVFL:	out of space for header keyword name list
IE_EOF:		end of file or list detected
.fi
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NOTES
An example illustrating the use of the keyword list package may be found
in imfort$tasks/phead.f.
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SEE ALSO
imtypk, imgkw
.endhelp
