Updates, structure changes

Author: V-Z

presentation/linux_bash_metacentrum_course.tex

@@ -495,7 +495,7 @@ \subsection{Basic theory of operating system}
 
 \begin{frame}{Types of files}
 \begin{itemize}
-  \item \bash/ls -la # See files and its types (below)/
+  \item \bash/ls -la/
   \item Regular file -- ordinary file, marked by \texttt{-}
   \item Directory -- in UNIX special type of file, marked by \texttt{d}
   \item Symbolic link (symlink, ``soft link'') -- points to another place, marked by \texttt{l}, slide \ref{links}
@@ -742,7 +742,7 @@ \subsection{Text}
     \item Show syntax highlight
     \item Show line numbers
     \item Show space between brackets
-    \item Open any encoding and EOL type
+    \item Open any encoding and EOL
     \item Fold source code
     \item Show line breaks
     \item Mark lines
@@ -773,6 +773,15 @@ \subsection{Text}
 \end{multicols}
 \end{frame}
 
+\begin{frame}{It \textbf{is} important to select \textbf{good} text editor\ldots}
+  \begin{center}
+    \includegraphics[width=\textwidth-1cm]{real_programmers.png}
+  \end{center}
+  \begin{flushright}
+    \url{https://xkcd.com/378/}
+  \end{flushright}
+\end{frame}
+
 \subsection{FISH}
 
 \begin{frame}{Friendly interactive shell}
@@ -876,12 +885,21 @@ \subsection{FISH}
 \end{frame}
 
 \begin{frame}[fragile]{The PATH variable}
-  \begin{bashcode}
-    #
-  \end{bashcode}
   \begin{itemize}
-    \item 
+    \item Lists directories (separated by colon \texttt{:}) where the current shell searches for commands
+    \item If some software is installed outside standard locations, the user must specify the full path (or update the \texttt{\$PATH})
+    \item In case there are two commands with the same name (e.g. \texttt{/bin/somecommand} and \texttt{/usr/bin/somecommand}), the order of directories in \texttt{\$PATH} matters -- the first occurrence is used, any possible later ignored
   \end{itemize}
+  \begin{bashcode}
+    # See the $PATH variable
+    echo $PATH # Sample output is on the next line:
+    /home/$USER/bin:/usr/local/bin:/usr/bin:/bin:/opt/bin:/sbin:/usr/sbin
+    # Adding new directory to $PATH
+    export PATH=$PATH:/some/new/directory # Ensure to add original $PATH
+    # Do not do it in the following way - it would overwrite $PATH, and
+    #   there would be only the new directory (not the original content)!
+    export PATH=/some/new/directory # Wrong! Old $PATH is missing!
+  \end{bashcode}
 \end{frame}
 
 \begin{frame}[fragile]{Reading variables from command line}
@@ -1004,7 +1022,7 @@ \subsection{FISH}
     ls -l .bash* # Numbers in first column show links pointing to it
                  # For directories - number of items, for files = 1
     -rw------- 1 vojta users 27298 21. led 16.43 .bash_history # One link
-    -rw-r--r-- 2 vojta users  2707 29. lis 16.21 .bashrc # Same data as below
+    -rw-r--r-- 2 vojta users  2707 29. lis 16.21 .bashrc # Same file as below
     -rw-r--r-- 2 vojta users  2707 29. lis 16.21 .bashrcX # Two links
   \end{bashcode}
 \end{frame}
@@ -1016,7 +1034,7 @@ \section{Command line}
   \item When you log off or network connection is broken, running tasks for particular terminal usually crash
   \item Sometimes number of connections is limited
   \item \texttt{screen} is solution -- virtual terminals
-  \item Launch \texttt{screen} to start new screen terminal, read some info, confirm by Space key or Enter
+  \item Launch \texttt{screen} to start new screen terminal, read some info, confirm by \textbf{Space key} or \textbf{Enter}
   \item To detach from the screen press \texttt{Ctrl+A, D} -- screen is still running in background -- you can even log off
   \item To return back to running screen use \texttt{screen -r} -- if only one screen is running, you get back to it
   \item If more screens are running, use \texttt{screen -r 1234} (the number is seen from \texttt{screen -r})
@@ -1041,7 +1059,7 @@ \section{Command line}
   \begin{bashcode}
     systemctl status/start/stop cron.service # Check/start/stop if cron runs
     crontab -l # List cron tasks
-    crontab -e # Edit cron tasks (launches editor according to the variable):
+    crontab -e # Edit cron tasks:
     # Minute, Hour, Day in month, Month, Day in week, Command (absolute path)
     # 0-59    0-23  1-31          1-12   0-6 starting with Sunday (WTF?)
       *       *     *             *      *            /usr/bin/command
@@ -1055,21 +1073,21 @@ \subsection{Chaining}
 
 \begin{frame}{Chaining commands}
 \begin{itemize}
-  \item \alert{\&} -- command will be launched in background, terminal is available for next typing: \texttt{firefox \&}
-  \item \alert{\&\&} -- second command is launched only when first command exits without error (exits with 0 status): \texttt{mkdir NewDir \&\& cd NewDir}
-  \item \alert{;} -- second command is launched regardless exit status of the first one: \texttt{kshfskcbd; hostname}
-  \item \alert{\textbraceleft\ldots\textbraceright} -- commands within curl brackets are launched as one block
-  \item \alert{||} -- second command is launched when first command fails (has non zero exit status):\\\texttt{cd newdir || \textbraceleft~mkdir newdir \&\& cd newdir; \textbraceright}
+  \item \alert{\texttt{\&}} -- command will be launched in background, terminal is available for next typing: \texttt{firefox \&} (when launching graphical application, hit \textbf{Enter} afterward if there is no active command line prompt)
+  \item \alert{\texttt{\&\&}} -- second command is launched only when first command exits without error (exits with status \texttt{0}): \texttt{mkdir NewDir \&\& cd NewDir}
+  \item \alert{\texttt{;}} -- second command is launched regardless exit status of the first one: \texttt{kshfskcbd; hostname}
+  \item \alert{\texttt{\textbraceleft\ldots\textbraceright}} -- commands within curl brackets are launched as one block
+  \item \alert{\texttt{||}} -- second command is launched when first command fails (has non zero exit status):\\\texttt{cd newdir || \textbraceleft~mkdir newdir \&\& cd newdir; \textbraceright}
   \item Behavior in shells other than bash might be little bit different
-  \item \alert{|} -- pipe -- redirects standard output of one command into standard input of second command: \texttt{ps aux | sort}
+  \item \alert{\texttt{|}} -- pipe -- redirects standard output of one command into standard input of second command: \texttt{ps aux | sort}
 \end{itemize}
 \end{frame}
 
 \begin{frame}[fragile]{Standard input and output and redirects}
 \begin{itemize}
   \item Standard input (\texttt{stdin}) is standard place where software takes input (keyboard and terminal) and writes results to standard output (\texttt{stdout}) -- typically monitor
   \item Standard error output (\texttt{stderr}) is target of error messages -- typically also monitor (but can be log file or so)
-  \item \alert{\textgreater} -- redirects output into new place (file, device, another command)
+  \item \alert{\texttt{\textgreater}} redirects output into new place (file, device, another command,~\ldots)
 \end{itemize}
   \begin{bashcode}
     cat /etc/group # Print whole file /etc/group
@@ -1078,7 +1096,7 @@ \subsection{Chaining}
     cat users # See result
   \end{bashcode}
 \begin{itemize}
-  \item \alert{\textgreater\textgreater} -- adds output to the end of the file (``\textgreater'' rewrites target file)
+  \item \alert{\texttt{\textgreater\textgreater}} adds output to the end of the file (\texttt{\textgreater} rewrites target file)
 \end{itemize}
   \begin{bashcode}
     grep root /etc/group >> users # Add new information into existing file
@@ -1105,10 +1123,10 @@ \subsection{Chaining}
     command >> outputfile 2>error.log
   \end{bashcode}
 \begin{itemize}
-  \item /dev/null -- ``black hole'' -- discards everything (don't care about errors?): \texttt{command 2\textgreater~/dev/null}
-  \item /dev/stdin -- standard input (in case application reads files, not from standard input): \texttt{echo "Žluťoučký kůň" | iconv -f utf-8 -t cp1250 /dev/stdin}
-  \item /dev/stdout -- standard output (we wish to see errors which would be discarded otherwise): \texttt{command 2\textgreater~/dev/stdout}
-  \item /dev/stderr -- standard error output (right place to send errors to): \texttt{echo "error" > /dev/stderr}
+  \item \texttt{/dev/null} -- ``black hole'' -- discards everything (don't care about errors?): \texttt{command 2\textgreater~/dev/null}
+  \item \texttt{/dev/stdin} -- standard input (in case application reads files, not from standard input): \texttt{echo "Žluťoučký kůň" | iconv -f utf-8 -t cp1250 /dev/stdin}
+  \item \texttt{/dev/stdout} -- standard output (we wish to see errors which would be discarded otherwise): \texttt{command 2\textgreater~/dev/stdout}
+  \item \texttt{/dev/stderr} -- standard error output (right place to send errors to): \texttt{echo "error" > /dev/stderr}
 \end{itemize}
 \end{frame}
 
@@ -1118,6 +1136,7 @@ \subsection{Information and management}
   \begin{bashcode}
     uname -a # Information about Linux kernel (version, ...)
     lsb_release -a # Information about Linux distribution release
+    cat /etc/os-release # Similar to above command
     lscpu # Information about CPU
     cat /proc/cpuinfo # Raw list of information about CPU
     lsusb # List of devices on USB
@@ -1132,6 +1151,7 @@ \subsection{Information and management}
     uptime # How long is the system running, number of users, average load
     date # Date and time - plenty of options for formatting
     mount # Information about mounted file systems
+    findmnt # Display mounted devices in tree structure
   \end{bashcode}
 \end{frame}
 
@@ -1158,24 +1178,6 @@ \subsection{Information and management}
   \end{bashcode}
 \end{frame}
 
-\begin{frame}[fragile]{Managing system services}
-\begin{itemize}
-  \item Different among distributions -- several main methods
-  \item Most common is SystemD, less common older init scripts and RC scripts
-  \item Used to manage services like web server, database, \ldots
-  \item \alert{Read documentation for your distribution!}
-  \item All actions require root authentication
-\end{itemize}
-  \begin{bashcode}
-    # SystemD - huge amount of possibilities
-    systemctl enable/disable/status/start/stop servicename # TAB helps
-    # RC scripts
-    rcservicename status/start/stop # TAB helps to select service
-    # Init scripts
-    /etc/init.d/servicename status/start/stop # TAB helps to select service
-  \end{bashcode}
-\end{frame}
-
 \begin{frame}[fragile]{Users}
   \begin{bashcode}
     whoami # What is my user name
@@ -1206,18 +1208,18 @@ \subsection{Directories}
     cd # Change directory (just "cd" or "cd ~" goes to home directory)
     cd .. # One directory up; cd ../..; cd ../../another/directory/
     cd relative/path/from/current/position # Go to selected directory
-    cd /absolute/path/from/root # Absolute path stars by "/"
+    cd /absolute/path/from/root # Absolute path starts by "/"
     tree # Tree like hierarchy of files and directories
     tree -d # List only directories; see tree --help
     tree -L 2 # Only up to second level; combine: tree -d -L 3
     du -sh # Disk usage by current directory, -s for sum, -h for nice units
-    mkdir # Make directory
-    rmdir # Remove empty directory
+    mkdir NewDirectory # Make directory
+    rmdir DirectoryToRemove # Remove empty directory
     ls # List directory content
        # Try parameters -l, -a, -1, -F, -h (with -l or -s), --help
     rm -r # Recursive delete - remove also non-empty directories
     mv from to # Move files/directories (also for renaming)
-    cp from to # Copy, -r (recursive, including subdirectories)        
+    cp from to # Copy, -r (recursive, including subdirectories)
                # -a (keeps all attributes), -v (verbose)
     file somefile # Information about questioned file (what it is, ...)
     xdg-open somefile # Open file by graphical application as in GUI
@@ -1230,9 +1232,9 @@ \subsection{Directories}
   \item \texttt{mc} to launch MC
   \item Move, copy, delete, files/directories, connect to SSH/(S)FTP, \ldots
   \item Can be used with mouse
-  \item Edit text files (F4)
-  \item F2 for quick menu
-  \item F9 for top menu with many possibilities
+  \item Edit text files (\texttt{F4})
+  \item \texttt{F2} for quick menu
+  \item \texttt{F9} for top menu with many functions
   \item And much more\ldots
   \item Not possible to live without it :-)
 \end{itemize}
@@ -1260,26 +1262,28 @@ \subsection{Archives}
 \begin{itemize}
   \item \texttt{gzip}, \texttt{bzip2} and \texttt{lzma} are able to pack only one file -- use them together with \texttt{tar} to pack multiple files
   \item \texttt{gzip}, \texttt{bzip2} and \texttt{lzma} when used \textbf{without} \texttt{tar} \alert{move} file into archive
-  \item \texttt{lzma} has excellent compression, but sometimes it is very slow
+  \item \texttt{lzma} has excellent compression, but sometimes is very slow
 \end{itemize}
 \end{frame}
 
 \begin{frame}{Compressing and decompressing archives}
-\begin{center}
-\begin{tabular}{llll}
-\textbf{Archive} & \textbf{Decompressing command}\\
-*.tar & tar xvf archive.tar\\
-*.tar.gz\alert{/}*.tgz & tar xzvf archive.tar.gz\alert{/}.tgz\\
-*.tar.bz\alert{/}*.tbz\alert{/}*.tar.bz2 & tar xjvf archive.tar.bz\alert{/}.tbz\alert{/}.tar.bz2\\
-*.tar.xz & lzcat archive.tar.xz | tar xvf -\\
-*.gz & gunzip archive.gz\\
-*.bz2 & bunzip2 archive.bz2\\
-*.xz & unlzma archive.xz\\
-*.zip & unzip archive.zip\\
-*.rar & unrar x archive.rar\\
-\end{tabular}
-\includegraphics[height=2cm]{tar.png}
-\end{center}
+  \begin{center}
+    \begin{tabular}{llll}
+      \textbf{Archive} & \textbf{Decompressing command}\\
+      *.tar & tar xvf archive.tar\\
+      *.tar.gz\alert{/}*.tgz & tar xzvf archive.tar.gz\alert{/}.tgz\\
+      *.tar.bz\alert{/}*.tbz\alert{/}*.tar.bz2 & tar xjvf archive.tar.bz\alert{/}.tbz\alert{/}.tar.bz2\\
+      *.tar.xz & lzcat archive.tar.xz | tar xvf -\\
+      *.gz & gunzip archive.gz\\
+      *.bz2 & bunzip2 archive.bz2\\
+      *.xz & unlzma archive.xz\\
+      *.zip & unzip archive.zip\\
+      *.rar & unrar x archive.rar\\
+    \end{tabular}
+  \end{center}
+  \includegraphics[height=2cm]{tar.png}
+  \hfill
+  \url{https://xkcd.com/1168/}
 \end{frame}
 
 \subsection{Searching}
@@ -1311,7 +1315,7 @@ \subsection{Searching}
     find photos/ -name *.jpg -exec mogrify -resize 1000x1000 '{}' \;
   \end{bashcode}
   \begin{itemize}
-    \item First \texttt{find}'s parameter is location, to search -- absolute or relative, ``\texttt{.}'' means current directory (the only compulsory parameter)
+    \item First \texttt{find}'s parameter is location to search -- absolute or relative, ``\texttt{.}'' means current directory (the only compulsory parameter)
     \item \texttt{-type} for only directories or only files (without this parameter, files as well as directories are looked for)
     \item \texttt{-name} supports wildcarts (\texttt{*}, \texttt{?} and \texttt{[\ldots]})
     \item \texttt{-print} is default action -- prints list of results