>>Why is -v the flag for "don't include" in grep? As user yread said, it's for inVert (the sense of the pattern match, from "matches" to "does not match"). You

>>Why is -v the flag for "don't include" in grep? As user yread said, it's for inVert (the sense of the pattern match, from "matches" to "does not match"). You're right, it is non-intuitive. One of the issues is that when you use single letter options, a particular letter could potentially stand more than one expanded word, e.g. in the case of v, it is more commonly used for Verbose or Version. Even there, it varies. Some commands use -v for version, others use -V (e.g. python does), and some use --version. GNU's long option format is a partial solution to that, but involves more typing. E.g. --verbose or --version or --invert. Also the command lines get longer then. No perfect solution as of now. You're right, over the years, with more and more people creating commands, and with no well-defined standard in the earlier years at least, the whole scene of command line tool names and options has become something of a mess. Later one some sort of standards and conventions have been created or evolved, informally, but not many command creators necessarily follow them. http://pubs.opengroup.org/onlinepubs/009696899/basedefs/xbd_chap12.html http://pubs.opengroup.org/onlinepubs/009696899/basedefs/xbd_... Also, they are pretty detailed, so it is somewhat time-consuming and complex to implement those guidelines in full.