UNIX COMMANDS

• pwd:'print working directory' displays the name of the current directory.
• cd:'change directory' command will change the current directory to the directory specified as the argument to the command.
• ls:'list files' command displays the files in a directory .
• ls-l:'long list option' for listing files displays permissions, links, owner, group, file size, modification date,file name.
• rm:'remove' command deletes ordinary files in a directory.
• mv:'move' commands moves a file from one location to another.It is also used to rename files,as in 'mv thisfile.txt thatfile.txt'
• cp:'copy' command creates a copy of a file.
• chmod: change mode command is used to control access rights to a file or files.
• mkdir: 'make directory' command creates a directory or sub directory within the current directory .
• rmdir: 'remove directory' command  removes a directory or sub directory. The specified directory must be empty before it can be removed.
• find:'find' command is used to locate files.
• file: 'file' command is used to determine the type of information in the file listed as the argument to the command, i.e..,text or binary.
• cat:'cat' command displays the content of files,.It is also used to concatenate files as in "cat file1.txt file2.txt file3.txt>allfiles.txt".
• wc: 'wc' command displays a count of characters, words, and lines in a text file.
• sort:'sort' command is used to sort and/or merge text files.
• grep:'grep' commands searches for text strings in files.
• who:tells who's logged on.
• finger username:gives you lots of information about that user.
• diff filename1 filename2: compares  files, and shows where they differ.
• cp filename1 filename2: copies a file.
• mv filename1 filename2: moves a file.
• date: shows the current date and time.
• cal: shows a calender of the current month.use eg..,'cal 10 2012, to get that for October 12, or 'cal 2012' to get the whole year.
• tail:used to display the last few lines of a file.
• head-lines file name:to display the first few lines of a file.
• cat file1 >>file2: append more than one file.