GNU Astronomy Utilities Operating mode options

Another group of options that are common to all the programs in Gnuastro are those to do with the general operation of the programs. The explanation for those that are not only limited to Gnuastro but are common to all GNU programs start with (GNU option).


(GNU option) Stop parsing the command-line. This option can be useful in scripts or when using the shell history. Suppose you have a long list of options, and want to see if removing some of them (to read from configuration files, see Configuration files) can give a better result. If the ones you want to remove are the last ones on the command-line, you do not have to delete them, you can just add -- before them and if you do not get what you want, you can remove the -- and get the same initial result.


(GNU option) Only print the options and arguments and abort. This is very useful for when you know the what the options do, and have just forgot their long/short identifiers, see --usage.


(GNU option) Print all options with an explanation and abort. Adding this option will print all the options in their short and long formats, also displaying which ones need a value if they are called (with an = after the long format followed by a string specifying the format, see Options). A short explanation is also given for what the option is for. The program will quit immediately after the message is printed and will not do any form of processing, see --help.


(GNU option) Print a short message, showing the full name, version, copyright information and program authors and abort. On the first line, it will print the official name (not executable name) and version number of the program. Following this is a blank line and a copyright information. The program will not run.


Do not report steps. All the programs in Gnuastro that have multiple major steps will report their steps for you to follow while they are operating. If you do not want to see these reports, you can call this option and only error/warning messages will be printed. If the steps are done very fast (depending on the properties of your input) disabling these reports will also decrease running time.


Print all necessary information to cite and acknowledge Gnuastro in your published papers. With this option, the programs will print the BibTeX entry to include in your paper for Gnuastro in general, and the particular program’s paper (if that program comes with a separate paper). It will also print the necessary acknowledgment statement to add in the respective section of your paper and it will abort. For a more complete explanation, please see Acknowledgments.

Citations and acknowledgments are vital for the continued work on Gnuastro. Gnuastro started, and is continued, based on separate research projects. So if you find any of the tools offered in Gnuastro to be useful in your research, please use the output of this command to cite and acknowledge the program (and Gnuastro) in your research paper. Thank you.

Gnuastro is still new, there is no separate paper only devoted to Gnuastro yet. Therefore currently the paper to cite for Gnuastro is the paper for NoiseChisel which is the first published paper introducing Gnuastro to the astronomical community. Upon reaching a certain point, a paper completely devoted to describing Gnuastro’s many functionalities will be published, see GNU Astronomy Utilities 1.0.


With this option, Gnuastro’s programs will read your command-line options and all the configuration files. If there is no problem (like a missing parameter or a value in the wrong format or range) and immediately before actually running, the programs will print the full list of option names, values and descriptions, sorted and grouped by context and abort. They will also report the version number, the date they were configured on your system and the time they were reported.

As an example, you can give your full command-line options and even the input and output file names and finally just add -P to check if all the parameters are finely set. If everything is OK, you can just run the same command (easily retrieved from the shell history, with the top arrow key) and simply remove the last two characters that showed this option.

No program will actually start its processing when this option is called. The otherwise mandatory arguments for each program (for example, input image or catalog files) are no longer required when you call this option.


Parse STR as a configuration file name, immediately when this option is confronted (see Configuration files). The --config option can be called multiple times in one run of any Gnuastro program on the command-line or in the configuration files. In any case, it will be immediately read (before parsing the rest of the options on the command-line, or lines in a configuration file). If the given file does not exist or cannot be read for any reason, the program will print a warning and continue its processing. The warning can be suppressed with --quiet.

Note that by definition, options on the command-line still take precedence over those in any configuration file, including the file(s) given to this option if they are called before it. Also see --lastconfig and --onlyversion on how this option can be used for reproducible results. You can use --checkconfig (below) to check/confirm the parsing of configuration files.


Print options and their values, within the command-line or configuration files, as they are parsed (see Configuration file precedence). If an option has already been set, or is ignored by the program, this option will also inform you with special values like --ALREADY-SET--. Only options that are parsed after this option are printed, so to see the parsing of all input options, it is recommended to put this option immediately after the program name before any other options.

This is a very good option to confirm where the value of each option is has been defined in scenarios where there are multiple configuration files (for debugging).


Accept option names in configuration files that start with the given prefix. Since order matters when reading custom configuration files, this option should be called before the --config option(s) that contain options with the given prefix. This option does not affect the options within configuration files that have the standard name (without a prefix).

This gives unique features to Gnuastro’s configuration files, especially in large pipelines. Let’s demonstrate this with the simple scenario below. You have multiple configuration files for different instances of one program (let’s assume nc-a.conf and nc-b.conf). At the same time, want to load all the option names/values into your shell as environment variables (for example with source). This happens when you want to use the options as shell variables in other parts of the your pipeline.

If the two configuration files have different values for the same option (as shown below), and you don’t use --config-prefix, the shell will over-write the common option values between the configuration files. But thanks to --config-prefix, you can give a different prefix for the different instances of the same option in different configuration files.

$ cat nc-a.conf

$ cat nc-b.conf

## Load configuration files as shell scripts (to define the
## option name and values as shell variables with values).
## Just note that 'source' only takes one file at a time.
$ for c in nc-*.conf; do source $c; done

$ astnoisechisel img.fits \
                 --config=nc-a.conf --config-prefix=a_
$ echo "NoiseChisel run with --tilesize=$a_tilesize"

$ astnoisechisel img.fits \
                 --config=nc-b.conf --config-prefix=b_
$ echo "NoiseChisel run with --tilesize=$b_tilesize"

Update the current directory configuration file for the Gnuastro program and quit. The full set of command-line and configuration file options will be parsed and options with a value will be written in the current directory configuration file for this program (see Configuration files). If the configuration file or its directory does not exist, it will be created. If a configuration file exists it will be replaced (after it, and all other configuration files have been read). In any case, the program will not run.

This is the recommended method111 to edit/set the configuration file for all future calls to Gnuastro’s programs. It will internally check if your values are in the correct range and type and save them according to the configuration file format, see Configuration file format. So if there are unreasonable values to some options, the program will notify you and abort before writing the final configuration file.

When this option is called, the otherwise mandatory arguments, for example input image or catalog file(s), are no longer mandatory (since the program will not run).


Update the user configuration file and quit (see Configuration files). See explanation under --setdirconf for more details.


This is the last configuration file that must be read. When this option is confronted in any stage of reading the options (on the command-line or in a configuration file), no other configuration file will be parsed, see Configuration file precedence and Current directory and User wide. Like all on/off options, on the command-line, this option does not take any values. But in a configuration file, it takes the values of 0 or 1, see Configuration file format. If it is present in a configuration file with a value of 0, then all later occurrences of this option will be ignored.


Only run the program if Gnuastro’s version is exactly equal to STR (see Version numbering). Note that it is not compared as a number, but as a string of characters, so 0, or 0.0 and 0.00 are different. If the running Gnuastro version is different, then this option will report an error and abort as soon as it is confronted on the command-line or in a configuration file. If the running Gnuastro version is the same as STR, then the program will run as if this option was not called.

This is useful if you want your results to be exactly reproducible and not mistakenly run with an updated/newer or older version of the program. Besides internal algorithmic/behavior changes in programs, the existence of options or their names might change between versions (especially in these earlier versions of Gnuastro).

Hence, when using this option (probably in a script or in a configuration file), be sure to call it before other options. The benefit is that, when the version differs, the other options will not be parsed and you, or your collaborators/users, will not get errors saying an option in your configuration does not exist in the running version of the program.

Here is one example of how this option can be used in conjunction with the --lastconfig option. Let’s assume that you were satisfied with the results of this command: astnoisechisel image.fits --snquant=0.95 (along with various options set in various configuration files). You can save the state of NoiseChisel and reproduce that exact result on image.fits later by following these steps (the extra spaces, and \, are only for easy readability, if you want to try it out, only one space between each token is enough).

$ echo "onlyversion X.XX"             > reproducible.conf
$ echo "lastconfig 1"                >> reproducible.conf
$ astnoisechisel image.fits --snquant=0.95 -P            \
                                     >> reproducible.conf

--onlyversion was available from Gnuastro 0.0, so putting it immediately at the start of a configuration file will ensure that later, you (or others using different version) will not get a non-recognized option error in case an option was added/removed. --lastconfig will inform the installed NoiseChisel to not parse any other configuration files. This is done because we do not want the user’s user-wide or system wide option values affecting our results. Finally, with the third command, which has a -P (short for --printparams), NoiseChisel will print all the option values visible to it (in all the configuration files) and the shell will append them to reproduce.conf. Hence, you do not have to worry about remembering the (possibly) different options in the different configuration files.

Afterwards, if you run NoiseChisel as shown below (telling it to read this configuration file with the --config option). You can be sure that there will either be an error (for version mismatch) or it will produce exactly the same result that you got before.

$ astnoisechisel --config=reproducible.conf

Some programs can generate extra information about their outputs in a log file. When this option is called in those programs, the log file will also be printed. If the program does not generate a log file, this option is ignored.

--log is not thread-safe: The log file usually has a fixed name. Therefore if two simultaneous calls (with --log) of a program are made in the same directory, the program will try to write to he same file. This will cause problems like unreasonable log file, undefined behavior, or a crash.


Use INT CPU threads when running a Gnuastro program (see Multi-threaded operations). If the value is zero (0), or this option is not given on the command-line or any configuration file, the value will be determined at run-time: the maximum number of threads available to the system when you run a Gnuastro program.

Note that multi-threaded programming is only relevant to some programs. In others, this option will be ignored.



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