Reads a spectrum either from a file specified by name or a file or pipe opened with the Tcl open command.
The next spectrum in the file parameter is read.
The file parameter can either be a path to a
file, or a handle returned from the Tcl open command.
If the file is a path, the file is opened, the first spectrum read,
and the file is closed. If the file parameter is a Tcl file
handle, the next spectrum at the current position in the file
is read, and the file remains open for further I/O.
A bit of history. Many years ago, there was a histogramming program that ran on the VMS operating system called SMAUG. It too had spectrum I/O facilities. Although SMAUG no longer exists, SpecTcl's sread command, as we will see, has been written to be able to exchange files with SMAUG. Most users do not know about or use the SMAUG interchange capabilities. All GUIs I know about only read/write ASCII formatted files.
-format fmt
Selects the format the file is in. SpecTcl supports a
simple ASCII format as well as SMAUG binary format.
fmt is a string that describes
which of these formats the file is in.
If fmt is ascii
nsclascii, the file is assumed to
be in SpecTcl's ASCII format. If fmt
is either binary or nsclbinary
the file is assumed to be in SMAUG binary format.
If not provided, the default format is nsclascii
-?no?snapshotDefines how the resulting spectrum is treated in SpecTcl once read in.
If -snapshot, the default,
is chosen, the spectrum is read into a
snapshot spectrum. Snapshot
spectra are spectra in every sense of the word, however
they are not connected to the histogramming kernel and
therefore never increment.
If -nosnapshot is supplied, once the
spectrum is read in, if the parameters the spectrum
was defined on exist in this intance of SpecTcl,
the spectrum is connected to the histogrammer and
will incrmement as new data arrives. Note that
only nsclascii (ascii)
spectra have information about which parameters
are in the spectrum and the underlying spectrum type.
Therefore -nosnapshot has no effect
for other spectrum formats.
If the SpecTcl is missing a definition for one or more of the parameters that are needed by the spectrum, the spectrum reverts to a snapshot spectrum.
-?no?replace
Determines what sread does if
a spectrum with the same name as the one in the file
is already defined. Note that this is orthogonal
to -snapshot.
If -noreplace (the default), if this
spectrum already exists a unique, similarly named
spectrum is created so that the existing spectrum is
not overwritten.
If -replace, existing spectra are
delted and overwritten with the spectrum from file.
-?no?bind
If -bind is present (by default it
is), once read in the spectrum is bound into display
shared memory. If -nobind the spectrum
is not bound into display memory. The spectrum can always
be bound later on using sbind.
Note that file substitutions don't work for sread. Since non command line options are provided, the format is nsclascii, a snapshot spectrum will be created, if necessary the spectrum's name will be changed to avoid overwriting an existing spectrum and the resulting spectrum is bound to display memory.
Example 2. Reading several spectra from one file
set file [open ~/test.asc r]
sread -format ascii $file
sread -format ascii $file
sread -format binary $file
close $file
If sread is pointed to a file it can only read one spectrum (the first). Using a file descriptor to identify the file allows several consecutive swrite commands to process consective spectra in the file.
Note there's no requirement the file not have other data sread can be freely mixed with e.g. read or gets as dictated by the contents of the file.
Example 3. Reading from a pipeline:
set file [open {|zcat ~/test.asc.gz} r]
sread -format ascii $file
sread -format ascii $file
sread -format ascii $file
close $file
In this case, ~/test.asc.gz is a file that has been compressed with gzip. Once a pipe has been formed with the decompressor we can just process spectra from the pipeline as we did for actual files.