3.5. Summary

On UNIX, as on Linux, all entities are in some way or another presented to the system as files with the appropriate file properties. Use of (predefined) paths allows the users and the system admin to find, read and manipulate files.

We've made our first steps toward becoming an expert: we discussed the real and the fake structure of the file system, and we know about the Linux file security model, as well as several other security precautions that are taken on every system by default.

The shell is the most important tool for interaction with the system. We learned several shell commands in this chapter, which are listed in the table below.

Table 3-10. New commands

Command	Meaning
bash	GNU shell program.
cat `file(s)`	Send content of file(s) to standard output.
cd `directory`	Enter `directory`. cd is a bash built-in command.
chgrp `newgroup` `file(s)`	Change the group ownership of `file(s)` to newgroup
chmod `mode` `file(s)`	Change access permissions on `file(s)`
chown `newowner`[:[newgroup]] `file(s)`	Change file owner and group ownership.
cp `sourcefile` `targetfile`	Copy `sourcefile` to `targetfile`.
df `file`	Reports on used disk space on the partition containing `file`.
echo `string`	Display a line of text
export	Part of bash that announces variables and their values to the system.
file `filename`	Determine file type of `filename`.
find `path` `expression`	Find files in the file system hierarchy
grep `PATTERN` `file`	Print lines in `file` containing the search pattern.
head `file`	Send the first part of `file` to standard output
id	Prints real and effective user name and groups.
info `command`	Read documentation about command.
less `file`	View `file` with a powerful viewer.
ln `targetfile` `linkname`	Make a link with name `linkname` to `targetfile`.
locate `searchstring`	Print all accessible files matching the search pattern.
ls `file(s)`	Prints directory content.
man `command`	Format and display online (system) manual pages for command.
mkdir `newdir`	Make a new empty directory.
mv `oldfile` `newfile`	Rename or move `oldfile`.
pwd	Print the present or current working directory.
quota	Show disk usage and limits.
rm `file`	Removes files and directories.
rmdir `file`	Removes directories.
tail `file`	Print the last part of `file`.
umask [`value`]	Show or change new file creation mode.
wc `file`	Counts lines, words and characters in `file`.
which `command`	Shows the full path to command.

We also stressed the fact that you should READ THE MAN PAGES. This documentation is your first-aid kit and contains the answers to many questions. The above list contains the basic commands that you will use on a daily basis, but they can do much more than the tasks we've discussed here. Reading the documentation will give you the control you need.