magick:tldr:b4e5c
This command is using a tool called "magick" to perform a certain operation on a set of input files.
Let's break down the command:
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"${*-jpg}" - This is using the shell parameter expansion syntax. It takes the value of the positional parameters passed to the script or command, and appends "-jpg" to the end of each parameter. So if you have multiple input files, like "file1", "file2", "file3", this part of the command will convert them into "file1-jpg", "file2-jpg", "file3-jpg".
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"+adjoin" - This is an option being passed to the "magick" tool. It tells the tool that the output files should be created separately for each input file. For example, if you have two input files, two separate output files will be created.
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"${page-%d-pdf}" - Similar to the previous step, this is using shell parameter expansion. It takes the input files and appends "-pdf" to the end of each, creating output file names like "file1-pdf", "file2-pdf", "file3-pdf". The "%d" is a placeholder that will be replaced with a numerical value corresponding to each input file. For example, if the input files are "file1", "file2", "file3", the resulting output files will be "file1-pdf", "file2-pdf", "file3-pdf".
In summary, this command takes a set of input files and uses the "magick" tool to convert them to JPEG format ("-jpg"), creating separate output files for each input file. Then it appends "-pdf" to the end of each input file, creating separate output files for each input file in PDF format.