Linux Command Summary Part 02 of 02

Linux Command Summary

Part 02 of 02

Pattern Matching with Grep

     The name grep is a contraction of get regular expression and print. Grep uses patterns which are known as regular expressions. Examples of regular expressions are.

          .                                  Any single character.

          \c                                A literal c character.

          [. . . ]                          Matches any one of the characters in the brackets.

          [c1-c2]                       Any character in the range c1−c2.

          [ˆc1-c2]                     Any character not in the range c1−c2.

          ˆ                                The start of a line.

          $                                The end of a line.

          expr*                         Matches zero or more copies of expr.

          expr1expr2                Matches the first expression followed by the second.

          expr1|expr2               Matches either the first or second expression.

          (. . . )                         Parentheses can be used for grouping.

Some examples:

          ˆ$                             Empty lines.

          ˆSTART$                 The word START on a line by itself.

          ˆ[0-9]                       Lines beginning with a digit.

          function                   Lines containing the word function.

Office-Style Applications

     There are a number of applications which provide the same kind of functionality as Microsoft Office. Documents can be exchanged with Office if they are saved in the correct format (e.g. .doc, .xls, . . . ). The following applications are part of the free software Open Office suite.

          oowriter                  Word processor.
          oocalc                     Spreadsheet.
          ooimpress               Powerpoint style presentations.
          oodraw                   Drawing program.
          oomath                   Equation editor.

In addition the following applications provide useful functionality.

          gnumeric                Spreadsheet.
          abiword                  Word processor.
          acrobat                    Adobe Acrobat reader.
          gsview                    PostScript viewer.
          scribus                    Page layout (like Pagemaker).

Graphics Applications

          gthumb                   Graphics viewing program.
          gimp                       Photoshop-like graphics program.
          xfig                        Vector-dsrawing program.

Data Processing Applications
     Our systems have a number of useful data processing applications installed.

          R                            Local statistics software.
          Splus                     A commercial version of R.
          sas                         A database system for corporations
                                        which does some statistics.
          perl                       A report generation language.
          awk                      An older report generation language.
          sed                       A non interactive (stream editor).

Software Development
     Unix is without peer when it comes to software development. Many developers produce software by developing it under Linux and simply cross-compiling for Windows.

           java                    Java runtime.
          cc                        C Compiler.
          c++                     C++ compiler.
          f77                      Fortran77 compiler.
          gfortran              Fortran95 compiler.
          python                A hot new scripting language.
          ruby                    A less hot new scripting language.
          tcl                       An older scripting language.
          umb-scheme      A scheme (aka Lisp) interpreter.
          octave                A language like Matlab.
          anjuta                A integrated C/C++ development environment.
          make                 A software build utility.

Linux Command Summary - Part 01

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Linux Command Summary Part 01 of 02

Linux Command Summary

Part 01 of 02

Basic Information

     The following commands can be used to find out basic information about the machine you are using.

         

          date                Print the time and date.

          cal                  Print a calendar.

          who                Show who is currently logged on to this machine.

          last                 Show who has logged in recently.

          uptime           Show how long the machine has been up.

          top                 Show the machine load and processes.

 (Type “q” to exit from top.)

Getting Help

     The following commands give access to a variety of on-line help systems.

          man cmd                The official on-line manual.

          man -k topic           Keyword search of the manual.

          apropos topic         Equivalent to man -k.

          gnome-help           The (graphical) Gnome help system.

          info                       The Gnu info system.

     The manual (either using the man command or through the gnome-help interface) should be the first place you use to obtain information about the system. The info command will get you access to a set of longer documents about some of the installed software.

The File System

     The Linux file system is organised as a set of nested containers called directories (or folders). Each directory can be used to hold other directories or files. The position of each file or directory is described by its pathname. This is a sequence of names separated by slashes (/).

      

          /dir1/dir2/. . ./dirn/filename

     At any given time there is a current working directory and simple names are taken to refer to files within this directory. File names can also be specified relative to the current directory using . to indicate the current directory and .. to indicate “up one level” from the current directory.

     There are a large number of commands related to obtaining information about files and directories in the system.

          pwd                     Print the path name of the current directory.

          cd dir                  Change the working directory to the one specified.

          ls                        List the names of the files in the current directory.

          ls -l                    List file names with additional information.

          du                      Report disk usage (in 1 kilobyte blocks).

          quota                 Report on disk usage and quota.

          wc                     Report lines, words and characters in a file.

          wc -l                 Report the number of lines in a file.

          wc -w               Report the number of words in a file.

Copying, Moving and Removing Files

     A number of commands can be used to copy and move files. Most of the file names here can be simple names or either relative or full pathnames.

          cp old new             Make a copy of a file under a new name.

          mv old new            Rename a file.

          cp files dir             Copy the specified files to the given directory.

          mv files dir            Move one or more files to a directory.

          rm files                  Remove the named files.

          rmdir dir                Remove the named (empty) directories.

          rm -r files              Recursively remove the named files and directories.

Redirecting Output

     The output of Linux commands can be redirected to and from files.

          cmd > file             Redirect output to the given file (overwrites).

          cmd >> file          Append output to the given file.

          cmd < file            Take input from the given file.

          cmd1 | cmd2        Output from one program into another (a “pipe”).

     The use of pipes is what makes Linux such a flexible system. For example,

          who | wc -l

     will count the number of users currently logged in.

Basic Operations on Files

          cat                     Concatenate and print files (on screen).

          tr                       Transliterate character sets.

          grep                   Print lines matching a pattern.

          sort                    Sort the lines of a file.

          head                  First few lines of a file.

          tail                    Last few lines of a file.

          more                 Page at a time display.

          less                   Alternative page at a time display.

     These programs can be combined using the redirection operations above. Here is how to concatenate three files together.

          cat file1 file2 file3 > combined

     Here is how to convert all uppercase letters in a file to lower case.

          tr [A-Z] [a-z] mixed > lcase

     Here is to find the lines in a file which contain the word Unix

          grep Unix file

     Find the number of lines which contain the word Unix.

          grep Unix file | wc -l

Linux Command Summary - Part 02

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Unix/Linux Command Reference

Unix/Linux Command Reference

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