So you've installed Slackware and you're staring at a terminal prompt, what now? Now would be a good time to learn about the basic command line tools. And since you're staring at a blinking curser, you probably need a little assistance in knowing how to get around, and that is what this chapter is all about.

Your Slackware Linux system comes with lots of built-in documentation for nearly every installed application. Perhaps the most common method of reading system documentation is by using the man(1). man (short for manual) will bring up the included man-page for any application, system call, configuration file, or library you tell it too. For example, man man will bring up the man-page for man itself. Unfortunately, you may not always know what application you need to use for the task at hand. Thankfully, man has built-in search abilities. Using the -k switch will cause man to search for every man-page that matches your search terms. The man-pages are organized into groups or sections by their content type. For example, section 1 is for user applications. man will search each section in order and display the first match it finds. Sometimes you will find that a man-page exists in more than one section for a given entry. In that case, you will need to specify the exact section to look in. In this book, all applications and a number of other things will have a number on their right-hand side in parenthesis. This number is the man page section where you will find information on that tool. darkstar:~$ man -k printf printf (1) - format and print data printf (3) - formatted output conversion darkstar:~$ man 3 printf Section Contents 1 User Commands 2 System Calls 3 C Library Calls 4 Devices 5 File Formats / Protocols 6 Games 7 Conventions / Macro Packages 8 System Administration

ls(1) is used to list files and directories, their permissions, size, type, inode number, owner and group, and plenty of additional information. For example, let's list what's in the / directory for your new Slackware Linux system. darkstar:~$ ls / bin/ dev/ home/ lost+found/ mnt/ proc/ sbin/ sys/ usr/ boot/ etc/ lib/ media/ opt/ root/ srv/ tmp/ var/ Notice that each of the listings is a directory. These are easily distinguished from regular files due to the trailing /; standard files do not have a suffix. Additionally, executable files will have an asterisk suffix. But ls can do so much more. To get a view of the permissions of a file or directory, you'll need to do a "long list". darkstar:~$ ls -l /home/alan/Desktop -rw-r--r-- 1 alan users 15624161 2007-09-21 13:02 9780596510480.pdf -rw-r--r-- 1 alan users 3829534 2007-09-14 12:56 imgscan.zip drwxr-xr-x 3 alan root 168 2007-09-17 21:01 ipod_hack/ drwxr-xr-x 2 alan users 200 2007-12-03 22:11 libgpod/ drwxr-xr-x 2 alan users 136 2007-09-30 03:16 playground/ A long listing lets you view the permisions, user and group ownership, file size, last modified date, and of course, the file name itself. Notice that the first two entires are files, and the last three are directories. This is denoted by the very first character on the line. Regular files get a "-"; directories get a "d". There are several other file types with their own denominators. Symbolic links for example will have an "l". Lastly, we'll show you how to list dot-files, or hidden files. Unlike other operating systems such as Microsoft Windows, there is no special property that differentiates "hidden" files from "unhidden" files. A hidden file simply begins with a dot. To display these files along with all the others, you just need to pass the -a argument to ls. darkstar:~$ ls -a .xine/ .xinitrc-backup .xscreensaver .xsession-errors SBo/ .xinitrc .xinitrc-xfce .xsession .xwmconfig/ Shared/ You also likely noticed that your files and directories appear in different colors. Many of the enhanced features of ls such as these colors or the trailing characters indicating file-type are special features of the ls program that are turned on by passing various arguments. As a convienience, Slackware sets up ls to use many of these optional arguments by default. These are controlled by the LS_OPTIONS and LS_COLORS environment variables. We will talk more about environment variables in chapter 5.

cd is the command used to change directories. Unlike most other commands, cd is actually not it's own program, but is a shell built-in. Basically, that means cd does not have its own man page. You'll have to check your shell's documentation for more details on the cd you may be using. For the most part though, they all behave the same. darkstar:~$ cd / darkstar:/$ls bin/ dev/ home/ lost+found/ mnt/ proc/ sbin/ sys/ usr/ boot/ etc/ lib/ media/ opt/ root/ srv/ tmp/ var/ darkstar:/$cd /usr/local darkstar:/usr/local$ Notice how the prompt changed when we changed directories? The default Slackware shell does this as a quick, easy way to see your current directory, but this is not actually a function of cd. If your shell doesn't operate in this way, you can easily get your current working directory with the pwd(1) command. (Most UNIX shells have configurable prompts that can be coaxed into providing this same functionality. In fact, this is another convience setup in the default shell for you by Slackware.) darkstar:~$ pwd /usr/local

While most applications can and will create their own files and directories, you'll often want to do this on your own. Thankfully, it's very easy using touch(1) and mkdir(1). touch actually modifies the timestamp on a file, but if that file doesn't exist, it will be created. darkstar:~/foo$ ls -l -rw-r--r-- 1 alan users 0 2008-01-18 15:01 bar1 darkstar:~/foo$ touch bar2 -rw-r--r-- 1 alan users 0 2008-01-18 15:01 bar1 -rw-r--r-- 1 alan users 0 2008-01-18 15:05 bar2 darkstar:~/foo$ touch bar1 -rw-r--r-- 1 alan users 0 2008-01-18 15:05 bar1 -rw-r--r-- 1 alan users 0 2008-01-18 15:05 bar2 Note how bar2 was created in our second command, and the third command simpl updated the timestamp on bar1 mkdir is used for (obviously enough) making directories. mkdir foo will create the directory "foo" within the current working directory. Additionally, you can use the -p argument to create any missing parent directories. darkstar:~$ mkdir foo darkstar:~$ mkdir /slack/foo/bar/ mkdir: cannot create directory `/slack/foo/bar/': No such file or directory darkstar:~$ mkdir -p /slack/foo/bar/ In the latter case, mkdir will first create "/slack", then "/slack/foo", and finally "/slack/foo/bar". If you failed to use the -p argument, man would fail to create "/slack/foo/bar" unless the first two already existed, as you saw in the example. Removing a file is as easy as creating one. The rm(1) will remove a file (assuming of course that you have permission to do this). There are a few very common arguments to rm. The first is -f and is used to force the removal of a file that you may lack explicit permission to delete. The -r argument will remove directories and their contents recursively. There is another tool to remove directories, the humble rmdir(1). rmdir will only remove directories that are empty, and complain noisely about those that contain files or sub-directories. darkstar:~$ ls foo_1/ foo_2/ darkstar:~$ ls foo_1 bar_1 darkstar:~$ rmdir foo_1 rmdir: foo/: Directory not empty darkstar:~$ rm foo_1/bar darkstar:~$ rmdir foo_1 darkstar:~$ ls foo_2 bar_2/ darkstar:~$ rm -fr foo_2 darkstar:~$ ls

Traditionally, UNIX and UNIX-like operating systems are filled with text files that at some point in time the system's users are going to want to read. Naturally, there are plenty of ways of reading these files, and we'll show you the most common ones. In the early days, if you just wanted to see the contents of a file (any file, whether it was a text file or some binary program) you would use cat(1) to view them. cat is a very simple program, which takes one or more files, concatenates them (hence the name) and sends them to the standard output, which is usually your terminal screen. This was fine when the file was small and wouldn't scroll off the screen, but inadequate for larger files as it had no built-in way of moving within a document and reading it a paragraph at a time. Today, cat is still used quite extensively, but predominately in scripts or for joining two or more files into one. darkstar:~$ cat /etc/slackware-version Slackware 12.0.0 Given the limitations of cat some very intelligent people sat down and began to work on an application to let them read documents one page at a time. Naturally, such applications began to be known as "pagers". One of the earliest of these was more(1), named because it would let you see "more" of the file whenever you wanted. more will display the first few lines of a text file until your screen is full, then pause. Once you've read through that screen, you can proceed down one line by pressing ENTER, or an entire screen by pressing SPACE. more is also capable of searching through a text file for keywords. Once you've displayed a file in more, simply press the / key and enter a keyword. Upon pressing ENTER, the text will scroll until it finds the next match. This is clearly a big improvement over cat, but still suffers from a serious flaw: more is not able to scroll back up through the file to allow you to read something you might have missed. Clearly a better solution is called for. In order to address the short-comings of more, a new pager was developed and ironically dubbed less(1). less is a very powerful pager that supports all of the functions of more while adding lots of additional features. To begin with, less allows you to use your arrow keys to controll movement within the document. Due to its popularity, many Linux distributions have begun to exclude more in favor of less. Slackware includes both. Moreover, Slackware also includes a handy little pre-processor for less called lesspipe.sh. This allows a user to exectute less on a number of non-text files. lesspipe.sh will generate text output from running a command on these files, and display it in less.

Links are a method of referring to one file by more than one name. By using the ln(1) application, a user can reference one file with more than one name. The two files are not carbon-copies of one another, but rather are the exact same file, just with a different name. To remove the file entirely, all of its names must be deleted. (This is actually the result of the way that rm and other tools like it work. Rather than remove the contents of the file, they simply remove the reference to the file, freeing that space to be re-used. ln will create a second reference or "link" to that file.) darkstar:~$ ln /etc/slackware-version foo darkstar:~$ cat foo Slackware 12.0.0 darkstar:~$ ls -l /etc/slackware-version foo -rw-r--r-- 1 root root 17 2007-06-10 02:23 /etc/slackware-version -rw-r--r-- 1 root root 17 2007-06-10 02:23 foo Another type of link exists, the symlink. Symlinks, rather than being another reference to the same file, are actually a special kind of file in their own right. These symlinks point to another file or directory. The primary advantage of symlinks is that they can refer to directories as well as files, and they can span multiple filesystems. These are created with the -s argument. darkstar:~$ ln -s /etc/slackware-version foo darkstar:~$ cat foo Slackware 12.0.0 darkstar:~$ ls -l /etc/slackware-version foo -rw-r--r-- 1 root root 17 2007-06-10 02:23 /etc/slackware-version lrwxrwxrwx 1 root root 22 2008-01-25 04:16 foo -> /etc/slackware-version When using symlinks, remember that if the original file is deleted, your symlink is useless; it simply points at a file that doesn't exist anymore.