Unix Commands, Generalities

We will use the typical Unix syntax for documenting commands and their options. The command and arguments presented in bold type are entered verbatim. File name(s) and user-supplied options are represented by terms such as name or file, with three dots signifying that more than one name may be given. The letter n refers to an integer option. Arguments enclosed in brackets [ ] are optional. A | separating arguments means ``or'': 

Unfortunately, Unix commands do not have a universal syntax (this probably reflects its heritage from and the organization of university research). In general, Unix commands are entered as:

The command is always the first word. The options modifying what the command does are usually one letter each and can be juxtaposed (grouped) into any order (as a test of the user's creativity in forming nonsense words). If the command operates on a file or several files, the filename(s) are given last.

This option syntax for commands is almost universal within Unix, but not quite. A few commands take options without the preceding dash while some commands accept dashes but do not require them. Some commands require a dash for each option separately, instead of permitting you to juxtapose several options after one dash. To check a command's syntax, refer to your local manual pages (possibly with the man command); or you can be experimental and try the command out on some temporary file you don't mind messing up a bit.

The following rules apply to all Unix commands and systems:

• Commands cannot be abbreviated (how can you with the few letters you have to begin with).
• Unix distinguishes between uppercase and lowercase letters for both commands and filenames. So the commands who, Who, and WHO are all different. Since standard Unix commands are lower case, who is the standard version.
• Unix shells use wild-card characters that allow you to select files without typing the complete name(s) of files. The two most useful wild-card characters are * and ?. The * is used to match any number of characters and the ? is used to match single characters. For example, 

  

• Unlike MS-DOS, the dot . has no special meaning in Unix. A file name can have one or more dots, so it is perfectly okay to have files named prog.f or prog.old.f. To Unix, . is just another character. There are, however, conventions * for naming files depending on the type of code contained in the file.
  

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  • Control-Key Commands *
  
  

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