Unix commands

Question: ls 

Answer:  lists your files

Question: ls -l 

Answer:  lists your files in 'long format', which contains lots of useful information, e.g. the exact size of the file, who owns the file and who has the right to look at it, and when it was last modified.

Question: ls -a 

Answer:  lists all files, including the ones whose filenames begin in a dot, which you do not always want to see.

Question: touch 

Answer:  The ‘$ touch’ command creates a file(not directory) and you can simple add an extension such as .txt after it to make it a Text File.

There are many more options, for example to list files by size, by date, recursively etc.

Question: more filename 

Answer:  shows the first part of a file, just as much as will fit on one screen. Just hit the space bar to see more or q to quit. You can use /pattern to search for a pattern.

Question: emacs filename 

Answer:  is an editor that lets you create and edit a file. See the emacs page.

Question: mv filename1 filename2 

Answer:  moves a file (i.e. gives it a different name, or moves it into a different directory 

Question: cp filename1 filename2 

Answer:  copies a file

Question: rm filename 

Answer:  removes a file. It is wise to use the option rm -i, which will ask you for confirmation before actually deleting anything. You can make this your default by making an alias in your .cshrc file.

Question: diff filename1 filename2 

Answer:  compares files, and shows where they differ

Question: wc filename 

Answer:  tells you how many lines, words, and characters there are in a file

Question: chmod options filename 

Answer:  lets you change the read, write, and execute permissions on your files. The default is that only you can look at them and change them, but you may sometimes want to change these permissions. For example, chmod o+r filename will make the file readable for everyone, and chmod o-r filename will make it unreadable for others again. Note that for someone to be able to actually look at the file the directories it is in need to be at least executable.

1. +w (stands for write and it changes file permissions to write) 

2. +r (stands for read and it changes file permissions to read) 

3. +x (generally it is used to make a file executable)

e.g. - $ chmod +w file.txt

$ chmod +r file.txt

$ chmod +x file.txt

Question: $ sort file 

Answer:  As the name suggests the ‘$ sort’ sorts the contents of the file according to the ASCII rules.

Question: $ history 

Answer:  The ‘$ history’ command is used to get list of previous commands may be obtained by executing the following command. you can also use parameters like !n to re-execute the nth command, !! to executes the most recent command, and !cp this will execute the most recent command that starts with cp.

Question: gzip filename 

Answer:  compresses files, so that they take up much less space. Usually text files compress to about half their original size, but it depends very much on the size of the file and the nature of the contents. There are other tools for this purpose, too (e.g. compress), but gzip usually gives the highest compression rate. Gzip produces files with the ending '.gz' appended to the original filename.

Question: gunzip filename 

Answer:  uncompresses files compressed by gzip.

Question: gzcat filename 

Answer:  lets you look at a gzipped file without actually having to gunzip it (same as gunzip -c).

Question: lpr filename 

Answer:  print. Use the -P option to specify the printer name if you want to use a printer other than your default printer. For example, if you want to print double-sided, use 'lpr -Pvalkyr-d', or if you're at CSLI, you may want to use 'lpr -Pcord115-d'. See 'help printers' for more information about printers and their locations.

Question: lpq 

Answer:  check out the printer queue, e.g. to get the number needed for removal, or to see how many other files will be printed before yours will come out

Question: lprm jobnumber 

Answer:  remove something from the printer queue. You can find the job number by using lpq. Theoretically you also have to specify a printer name, but this isn't necessary as long as you use your default printer in the department.

Question: genscript 

Answer:  converts plain text files into postscript for printing, and gives you some options for formatting. Consider making an alias like alias ecop 'genscript -2 -r \!* | lpr -h -Pvalkyr' to print two pages on one piece of paper.

Question: dvips filename 

Answer:  print .dvi files (i.e. files produced by LaTeX). You can use dviselect to print only selected pages. See the LaTeX page for more information about how to save paper when printing drafts.

Question: mkdir dirname 

Answer:  make a new directory

Question: rmdir 

Answer:  The ‘$ rmdir’ command deletes any directory we want to delete and you can remember it by its names ‘rmdir’ which stands for ‘remove directory’.

Question: cd dirname 

Answer:  change directory. You basically 'go' to another directory, and you will see the files in that directory when you do 'ls'. You always start out in your 'home directory', and you can get back there by typing 'cd' without arguments. 'cd ..' will get you one level up from your current position. You don't have to walk along step by step - you can make big leaps or avoid walking around by specifying pathnames.

Question: pwd 

Answer:  tells you where you currently are.

Question: ff 

Answer:  find files anywhere on the system. This can be extremely useful if you've forgotten in which directory you put a file, but do remember the name. In fact, if you use ff -p you don't even need the full name, just the beginning. This can also be useful for finding other things on the system, e.g. documentation.

Question: grep string filename(s) 

Answer:  looks for the string in the files. This can be useful a lot of purposes, e.g. finding the right file among many, figuring out which is the right version of something, and even doing serious corpus work. grep comes in several varieties (grep, egrep, and fgrep) and has a lot of very flexible options. 

Question: who 

Answer:  tells you who's logged on, and where they're coming from. Useful if you're looking for someone who's actually physically in the same building as you, or in some other particular location.

Question: finger username 

Answer:  gives you lots of information about that user, e.g. when they last read their mail and whether they're logged in. Often people put other practical information, such as phone numbers and addresses, in a file called .plan. This information is also displayed by 'finger'.

Question: last -1 username 

Answer:  tells you when the user last logged on and off and from where. Without any options, last will give you a list of everyone's logins.

Question: talk username 

Answer:  lets you have a (typed) conversation with another user

Question: write username 

Answer:  lets you exchange one-line messages with another user

Question: elm 

Answer:  lets you send e-mail messages to people around the world (and, of course, read them). It's not the only mailer you can use, but the one we recommend. See the elm page, and find out about the departmental mailing lists (which you can also find in /user/linguistics/helpfile).

Question: whoami 

Answer:  returns your username. Sounds useless, but isn't. You may need to find out who it is who forgot to log out somewhere, and make sure *you* have logged out.

Question: date 

Answer:  shows the current date and time.

Question: cal 

Answer:  shows a calendar of the current month.

Question: man commandname 

Answer:  shows you the manual page for the command

Question: echo $VARIABLE 

Answer:  shows the value of an environment variable