Unix commands are abbreviations and sometimes cryptic. They can be two, three, or four letters long. For example, rm, cp, and lpr are frequently used. In addition, there may be options, called switches, parameters, and redirection symbols. You must separate the command and its options with spaces. Think of the command as a verb and the options as objects. Unlike MS Windows, lower case letters are not the same as upper case letters. Most commands and options are given in lower-case letters.
Not all commands need switches. Switches usually begin with a minus sign, but a plus sign may be used to turn on an option. Of course, a space separates the switch from the command. Parameters, which are usually file names, follow the switches if they are present or the command itself if not. Again, a space is needed before the parameter. If there are several file names, they are placed one after the other (and separated by spaces). If a group of file names has common letters, you can specify to the entire group with one name that contains the * and ? wild cards. For example, the parameter *plt refers to all files that end in the three letters plt. You can also use square brackets to select particular characters. For example, the option beam[1-3,56] (with no spaces) chooses beam1, beam2, beam3, beam5, and beam6.
The output redirection symbol, >, sends information destined for the video screen to a file instead. Similarly, the input redirection symbol, <, gets information that you normally type from the keyboard from a disk file instead. For example, the line:ansys < infile.a > outfileruns the ansys program and feeds it the information from the disk file named infile.a and puts the program output into the file named outfile. The command:cat file1 file2 > file3combines the two files file1 and file2 and puts the result into a new file named file3. You can find out more about a command with the man (for manual) command. For example, the command man cp tells about the cp command. The following Unix commands are frequently needed.cd matlab change to the subdirectory named matlab cd change to the home directory cp file1 file2 make a copy of file1 called file2 cp dir2/file1 . copy file1 from directory dir2 into current directory diff file1 file2 show differences between files echo $param show idefinition of param env show values of environment variables history show previous commands by number lpr -Pserver f1 print file f1 on server (notice capital P) -Zduplex two-sided printing -#10 print 10 copies lpq -Pworkman54 look at printer queue for sage ls *dwg list names of all files ending in the letters dwg man cp learn more about cp command (manual) mkdir dir make a new directory called dir more file1 look at file1 page by page (usually aliased to just m) mv file1 file2 move or rename file1 to file2 passwd change password pwd show current directory name quota your file size rm *bak remove all files ending in the letters bak abbr=orig define abbreviation (usually shorter) tail -15 file1 look at last 15 lines of file1You can rerun previous commands and make changes with emacs commands:^P redisplay previous command (then use commands to change it) ^Rls repeat most recent command that begins with ls !5 repeat command 5 (use history or h to find the command number) !^ first option of previous command !$ last option of previous command !* all options of previous command !:2 second option of previous commandBefore erasing files, check that the parameters are correct. For example, first give:ls fname* # list corresponding files rm !$ # erase those filesTo copy files from my class directory, define a short symbol a, then check that it is correct before using it.a=~es421/class # define shorter symbol a echo $a # check definition copy $a/files . # copy files (don't forget the dot)
Also see: TCC Unix help, alias and function definitions
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Last revised: January 6, 2004