The Growth of Command Line Options, 1979-Present


    Dan Luu, writing in a blog post: The sleight of hand that’s happening when someone says that we can keep software simple and compatible by making everything handle text is the pretense that text data doesn’t have a structure that needs to be parsed4. In some cases, we can just think of everything as a single space separated line, or maybe a table with some row and column separators that we specify (with some behavior that isn’t consistent across tools, of course). That adds some hassle when it works, and then there are the cases where serializing data to a flat text format adds considerable complexity since the structure of data means that simple flattening requires significant parsing work to re-ingest the data in a meaningful way. Another reason commands now have more options is that people have added convenience flags for functionality that could have been done by cobbling together a series of commands. These go all the way back to v7 unix, where ls has an option to reverse the sort order (which could have been done by passing the output to tac). […] Over time, more convenience options have been added. For example, to pick a command that originally has zero options, mv can move and create a backup (three options; two are different ways to specify a backup, one of which takes an argument and the other of which takes zero explicit arguments and reads an implicit argument from the VERSION_CONTROL environment variable; one option allows overriding the default backup suffix). mv now also has options to never overwrite and to only overwrite if the file is newer. mkdir is another program that used to have no options where, excluding security things for SELinux or SMACK as well as help and version options, the added options are convenience flags: setting the permissions of the new directory and making parent directories if they don’t exist. If we look at tail, which originally had one option (-number, telling tail where to start), it’s added both formatting and convenience options For formatting, it has -z, which makes the line delimiter null instead of a newline. Some examples of convenience options are -f to print when there are new changes, -s to set the sleep interval between checking for -f changes, –retry to retry if the file isn’t accessible. Read more of this story at Slashdot.


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