In fact, -output can be shortened to -o curl -o my.file -s Many options for many tools have a shortened alias. There are many, many more options, but for now, we know how to use curl to do something that is actually quite powerful: fetch a file, anywhere on the Internet, from the simple confines of our command-line.īefore we go further, though, let's look at the various ways this simple command can be re-written and, more crucially, screwed up: Shortened optionsĪs you might have noticed in the -silent documentation, it lists the alternative form of -s. So those are the basics for the curl command. It will still output the data you ask for, potentially even to the terminal/stdout unless you redirect it. Don't show progress meter or error messages. In curl's documentation of options, there is an option for silence: The curl progress indicator is a nice affordance, but let's just see if we get curl to act like all of our Unix tools. As far as the computer cares, it just joins the two lines together as if that backslash weren't there and runs it as one command. This is solely to make it easier for you to read. In this case, the command is so long (because of the URL) that I broke it down into two lines with the use of the backslash, i.e. Quick note: If you're new to the command-line, you're probably used to commands executing every time you hit Enter. Let's try it with a bigger file (this is the baby names file from the Social Security Administration) to see how the progress indicator animates: curl \ For a very small file, that status display is not terribly helpful. In the example of curl, the author apparently believes that it's important to tell the user the progress of the download. Rule of Silence: When a program has nothing surprising to say, it should say nothing. If you remember the Basics of the Unix Philosophy, one of the tenets is: Let's back up a bit: when you first ran the curl command, you might have seen a quick blip of a progress indicator: % Total % Received % Xferd Average Speed Time Time – you will the HTML that powers I thought Unix was supposed to be quiet? Using the ls command will show the contents of the directory: lsĪnd if you use cat to output the contents of my.file, like so: cat my.file So let's confirm that a file named my.file was actually downloaded. Let's try it with a basic website address: curl -output my.fileīesides the display of a progress indicator (which I explain below), you don't have much indication of what curl actually downloaded. That -output flag denotes the filename ( some.file) of the downloaded URL ( ) This is the basic usage of curl: curl -output some.file Other times we might pipe it directly into another program. Sometimes we want to save a web file to our own computer. The curl tool lets us fetch a given URL from the command-line. Syntax:Ĭontrols contours in the current frame.How to download files straight from the command-line interface A valid contrast value is from 0 to 10 and bias value from 0 to 1. Syntax:Ĭontrols the colormap for the current frame. $ds9 -catalog symbol 2 shape "boxcircle point" $ds9 -catalog symbol condition '\$Jmag>15' $ds9 -catalog match # last two catalogs loaded condition|shape|color|text|font|fontsize|fontweight|fontslant ] All other commands operated on the last search created, unless indicated otherwise. The first three commands will create a new catalog search. Syntax:įor RGB frames, sets the current color channel to blue. Syntax:Ĭontrols binning factor, binning buffer size, and binning function for binning FITS bin tables. Select ASINH scale function for the current frame. $ds9 -analysis 0 # invoke first analysis task Can also be used to display a message and display text in the text dialog window. Tasks are numbered as they are loaded, starting with 0. Syntax:Ĭontrols the World Coordinate System alignment for the current frame. Next, bar.fits is loaded and the colormap for bar.fits is changed to I8. Then the colormap for foo.fits is changed to Heat and the scale changed to zscale. For example, the following command line option is used: $ds9 -tile foo.fits -cmap Heat -zscale bar.fits -cmap I8įirst DS9 is put in tile mode, then foo.fits is loaded. Therefore, it is possible to use command line options as a little script. Command Line Options Command Line OptionsĭS9 will process each command line option, one at a time, as the last step in the initialization process.
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