#Bash grep output file timestamp archive

^ caret is used to search for a pattern that only occurs at the beginning of a line.īy default, grep is case sensitive, which means you have to be precise in the capitalization of your search string. We get the same output as before, but the command is much easier to type, especially if we had a bigger range of numbers or letters. brackets with a hyphen can be used to specify a range of characters, either numerical or alphabetical. This command will return any lines that say ‘Class 1’, ‘Class2’, or ‘Class 3’. brackets are used to match any of a set of characters. Several exist, and we will go over some of the most commons ones in the examples below: Grep’s functionality is further extended by using regular expressions, allowing you more flexibility in your searches.

Knowing this little trick is especially useful when greping through configuration files in Linux since tabs are frequently used to separate commands from their values. Normally, pressing tab in a terminal window tells the terminal that you want to auto-complete a command, but pressing the ctrl+v combination beforehand will cause the tab character to be written out as you’d normally expect it to in a text editor.

It’s handy to use grep to find a file when you use it to search through the output of the ls command as we showed in the first examples of the tutorial. Difference between find and grepįor those just starting out on the Linux command line, it’s important to remember that find and grep are two commands with two very different functions, even though we use both to “find” something that the user specifies. We mention this because files compressed with gzip are very commonly tar archives. Zgrep also works on tar files, but only seems to go as far as telling you whether or not it was able to find a match.

#Bash grep output file timestamp archive

It allows you to search the files inside of a compressed archive without having to first decompress that archive, basically saving you an extra step or two. You can use zgrep to search compressed files for a pattern. You could use this information to kill a running process or troubleshoot issues with the services running on your system. This is similar in function to just piping the output of the ‘ps’ command to grep. $ ls | grep DocumentsĪs you can see in the screenshot above, using the grep command saved us time by quickly isolating the word we searched for from the rest of the unnecessary output that the ls command produced. Let’s look in our home directory for a folder called Documents.Īnd now, let’s try checking the directory again, but this time using grep to check specifically for the Documents folder. That’s something you would use the “ls” command for.īut, to make this whole process of checking the directory’s contents even faster, you can pipe the output of the ls command to the grep command. Say that you need to check the contents of a directory to see if a certain file exists there. Let’s look at some really common examples. You can use it to search a file for a certain word or combination of words, or you can pipe the output of other Linux commands to grep, so grep can show you only the output that you need to see. When logging, it's good to have timestamp.Grep is a command-line tool that Linux users use to search for strings of text. To save, call write-file.įor a detailed tutorial, see: Emacs Shell Tutorial (Bash, cmd.exe, PowerShell) Start emacs, then call shell to start shell. That way, you don't have to worry whether you forgot to start to log it. (whether exit shell or Ctrl+ dĬloses the window/tab depends on your terminal app.)īest is to use shell inside emacs. Type exit, it exits your shell, and closes the terminal window,Īnd you lose all data. Sometimes you don't remember if you started “script” or not, and if you

The command exit to stop logging is a problem, because.You page up and down several times, all the screen text are logged. For example, you started to view a man page, and It contains lots control sequences, itĪlso contain man page. Start logging like this script ~/session.log. This is a nice solution, but the problem is, in some dumb terminal such as Ctrl+Alt+F1 Virtual Console, there's no menu or copy and paste. Then, when you need to save session, just pull menu, then menu, then paste it in a editor. If your terminal doesn't have unlimited/infinite option, just use a big number. To set unlimited scrollback, in gnome-terminal, it's under menu tab. One way is set your terminal to unlimited scrollback, then, just select all, copy, then paste and save in a editor. Set Terminal Scrollback to Unlimited, Copy and Save If you do a lot sys admin work, or you want a record of your shell session, you can log it to a file.