The command-line is the interactive interface to your shell.

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19
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6answers
752 views

Why is aliasing over standard commands not recommended?

For example, a common alias I've seen in the ~/.bashrc file (or equivalents) is alias rm='rm -i' However, I've seen people recommend against this because the alias might not exist on another ...
19
votes
2answers
1k views

Coloring different sources for tail

I'm watching different logs by tail -q -f /var/log/syslog -f /var/log/fail2ban.log -f /var/log/nginx/error.log How can I have the output of each log colored differently?
19
votes
3answers
5k views

Command for forcing a pointer ungrab (captured mouse release)

Sometimes Firefox doesn't release the mouse after dragging, so I need to kill the application to force it to release its pointer grab. Is there any command to force an application to ungrab the ...
19
votes
2answers
8k views

Is it possible to save as sudo from nano after you've forgotten to run as sudo?

A lot of the time I edit a file with nano, try to save and get a permission error because I forgot to run it as sudo. Is there some quick way I can become sudo without having to re-open and re-edit ...
18
votes
6answers
803 views

How stable are Unix shell “stdin/stdout APIs”?

grepping, awking, sedding, and piping are day-to-day routine of a user of any Unix-like operating system, may it be on the command line or inside a shell script (collectively called filters from now ...
18
votes
5answers
864 views

Difference between “. myscript” and “./myscript” [duplicate]

I am confused by "one only dot - space - shell script name" (like . myshellscript) and "path to shell script" (like ./myshellscript) commands. What for they are? I noticed the command . myshellscript ...
18
votes
3answers
7k views

how to download a file using just bash and nothing else (no curl, wget, perl, etc.)

I have a minimal headless *nix which does not have any command line utilities for downloading files (e.g. no curl, wget, etc). I only have bash. How can I download a file? Ideally, I would like a ...
18
votes
2answers
88k views

Zip all files in directory?

Is there a way to zip all files in a given directory with the zip command? I've heard of using *.*, but I want it to work for extensionless files, too.
18
votes
8answers
1k views

How to tell what type of filesystem you're on?

Is there a command to tell what type of filesystem you're using?
18
votes
7answers
46k views

What is the fastest way to view images from the terminal?

The terminal is very fast and convenient way to quickly access directories and files (faster than find and click on the directory). One thing that it cannot show in text-mode is "pictures". What ...
18
votes
6answers
17k views

Sorting files according to size recursively

how to scan a folder recursively and find the largest files in the folder, and sort them by size. I have tried using ls -R -S but it tends to list the directories as well I need to scan the folders ...
18
votes
6answers
3k views

put history command onto command line without executing it

I use !n where (n) is the line number for executing a line in the history file I want executed at the command prompt which I find via history|less. But there is a command line history event I wish ...
18
votes
1answer
2k views

zsh Interpret/ignore commands beginning with '#' as comments

In bash, if I type a command beginning with a '#', bash ignores it as a comment. Ie, the following is ignored at the bash prompt: > # Hi there! Whereas in zsh: > # Hi there ! zsh: bad ...
18
votes
1answer
815 views

Is there a standard command that always exits with a failure?

I want to test my script with a command that fails. I could use an existing command with bad arguments. I could also write a simple script that immediately exits with a failure. Both of these are easy ...
18
votes
7answers
3k views

Command-line-friendly full-text indexing?

Is there such a thing as a full-text indexing engine, that can be queried from the command line and ideally wouldn't require using a gui at all ? I'm especially interested in indexing my ebooks and ...
17
votes
5answers
2k views

Why do I sometimes get repeatedly prompted with “>” in the terminal?

Alright, when I run certain commands the wrong way, (misspelled, etc.) The terminal outputs this: > instead of computername:workingfolder username$, and when I type enter it goes like this: > ...
17
votes
6answers
7k views

How to display numbers in reverse order using seq(1)?

I have iterate over numbers in various order. I am able to display them in increasing order, even with steps like: $ seq --separator="," 1 10 1,2,3,4,5,6,7,8,9,10 $ seq --separator="," 1 2 10 ...
17
votes
9answers
2k views

How to make sure that a command is not interrupted, even if terminal is closed? [duplicate]

In Linux. Say I want to run a command and it takes too long. I just want to ensure it's done. How?
17
votes
6answers
2k views

Why do I have to cd out of a deleted directory?

On my server I have a directory structure looking something like this: /myproject/code I normally have an ssh connection to the server and 'stand' in that directory: root@machine:/myproject/code# ...
17
votes
2answers
21k views

How to signal the end of stdin input in bash

In Bash, I learned that the ending signal can be changed by here document. But by default how can I signal the end of stdin input? I happened to find that with cat and chardet, their stdin inputs can ...
17
votes
2answers
45k views

How to display open file descriptors but not using lsof command

Hi I have read Here that lsof is not an accurate way of getting the number of File Descriptors that are currently open. He recommended to use this command instead cat /proc/sys/fs/file-nr While ...
17
votes
2answers
2k views

How did this '&' at the end of my command, make the script SO fast?

While solving some CTF challenges online, I came across a situation where I needed to bruteforce a server. This is the code I wrote: #!/bin/bash for i in {0..9}{0..9}{0..9}{0..9} do echo ...
17
votes
2answers
931 views

^x^y unix trick for all instances in last command?

One of my favorite Unix tricks is ^x^y, which will take the last command and replace the first instance of "x" with "y". However, I'm wondering if a similar trick works to replace all instances of "x" ...
17
votes
2answers
445 views

Is there a standard Unix command to check English verb conjugation?

Having recently come across wordlist and wordnet, two great discoveries on their own, I'm now looking for a similar tool, if simpler, that will take the bare infinitive of a verb and return the simple ...
17
votes
1answer
3k views

copy (to X clipboard) shortcut in .tmux.conf

In order to copy text to X clipboard in tmux, what I currently do is: go selection mode with prefix[ start selection with space (using mode-keys vi btw) select the text and press enter copy tmux ...
16
votes
2answers
2k views

Create a test file with lots of zero bytes

I know how to create an empty file: touch /var/tmp/nullbytes but how can I create a 1MB file that only contains nullbytes on the commandline with bash?
16
votes
6answers
735 views

How to type several file names with fewer key strokes

If I want to convert a pdf to a png image with imagemagick I do something like: convert -trim -density 400 this_is_a_very_long_filename_of_my_pdf_file.pdf ...
16
votes
10answers
18k views

What's a good example of piping commands together?

If you were helping someone to learn the concept of pipes on the command line what example would you use? The example that actually came up was as follows: cat whatever.txt | less I feel like ...
16
votes
4answers
601 views

How can I implement a circular flow of data among interconnected commands?

I know of two types how commands can be connected with each other: by using a Pipe (putting std-output into std-input of the next command). by using a Tee (splice the output into many ...
16
votes
7answers
3k views

How to efficiently generate large, uniformly distributed, random integers in bash?

I have been wondering what would be the best way to get good randomness in bash, i.e., what would be a procedure to get a random positive integer between MIN and MAX such that The range can be ...
16
votes
2answers
9k views

Break a large file into smaller pieces

How do I break a large, +4GB file into smaller files of about 500MB each. And how do I re-assemble them again to get the original file?
16
votes
3answers
3k views

IP to Country console command

Is there a console command that takes an IP address as an input and shows its geographical information like city, country, ISP, etc.?
16
votes
2answers
497 views

How to retrieve lost aliases?

Let me start by saying I know this was dumb. Time and Linux make fools of us all. I made an echo command to my .bash_aliases file and erased all of my aliases, except the test alias. However, I ...
16
votes
1answer
15k views

How to display kernel command line parameters?

In the grub.conf configuration file I can specify command line parameters that the kernel will use, i.e.: kernel /boot/kernel-3-2-1-gentoo root=/dev/sda1 vga=791 After booting a given kernel, is ...
16
votes
4answers
2k views

Is it possible to configure ctrl-w (delete word)?

Normally, Ctrl-w deletes back to the last whitespace. Is it possible to configure it to use additional characters, such as /? Edit: To be more clear: I don't want to configure the key for it, I want ...
16
votes
2answers
5k views

How to execute consecutive commands from history?

Suppose I want to execute a sequence of four commands that I have executed before. If the first one is 432 in the command-history, then I could do: $ !432; !433; !434; !435 I'm curious, is there a ...
16
votes
2answers
1k views

Is it harmful to close a terminal window without properly exiting an application?

Using Ubuntu 12.04 LTS, my question is that if I started an application in a terminal window, then is there anything bad about just closing the terminal window without exiting the application properly ...
16
votes
1answer
9k views

What do double slashes mean in UNIX path? Is `cd dir/subdir//` valid? [duplicate]

Possible Duplicate: How linux handles multiple path separators (/home////username///file) Do cd dir/subdir/ and cd dir/subdir// mean the same in UNIX? Will the later work out? Else does ...
16
votes
1answer
4k views

How do we specify multiple ignore patterns for `tree` command?

I need to print the directory structure of our production system and I would like to remove some specific directories from the tree? How do we specify multiple ignore patterns for tree command?
16
votes
3answers
7k views

How do I find the window dimensions and position accurately including decorations?

I've been trying to figure out the size of a window for use in a small script. My current technique is using wmctrl -lG to find out the dimensions. However, the problem is this: The x and y figures ...
16
votes
4answers
1k views

Copy image from command-line to clipboard

Is there a way in a bash to copy a picture to the clipboard? For example if there is a picture mypic.png I want to have a command like clipcopy mypic.png such that I can go for example to inkscape ...
15
votes
3answers
3k views

Why isn't there any shell command to create files?

Attention please: I am not asking how to make a file from the command line! I have been using touch for making files for years without paying attention that its main purpose is something else. If ...
15
votes
5answers
24k views

Linux ls to show only filename date and size

How can I use ls in linux to get a listing of filenames date and size only. I don't need to see the other info such as owner or permission. Is this possible?
15
votes
5answers
13k views

How can I see dmesg output as it changes?

I'm writing a device driver that prints error message into ring buffer dmesg output. I want to see the output of dmesg as it changes. How can I do this?
15
votes
4answers
5k views

Why do some commands 'hang' the terminal until they've finished?

Sometimes you run a program from the terminal, say, lxpanel†. The terminal won't drop you back to the prompt, it'll hang. You can press Ctrl+C to get back to the prompt, but that will kill ...
15
votes
3answers
17k views

How to cause kernel panic with a single command?

Is it possible to cause a kernel panic with a single command line? What would be the most straightforward such command for a sudoing user and what would it be for a regular user, if any? Scenarios ...
15
votes
4answers
13k views

How can I get a formatted date for a UNIX timestamp from the command line

I have a UNIX timestamp and I'd like to get a formatted date (like the output of date) corresponding to that timestamp. My attempts so far: $ date +%s 1282367908 $ date -d 1282367908 date: invalid ...
15
votes
2answers
2k views

How can I count the number of different characters in a file?

I would need a program, that outputs the number of the different characters in a file. Example: > stats testfile ' ': 207 'e': 186 'n': 102 Exists any tool, that do this?
15
votes
1answer
582 views

Make program first read from pipe, then from keyboard

Consider the interactive program interactive. I have to run this program fairly frequently, and each time I run it the first few commands are the same. Obviously, having to type those commands over ...
15
votes
3answers
706 views

Why don't shell builtins have proper man pages?

All shell builtins share the same manual page: BUILTIN(1) BSD General Commands Manual BUILTIN(1) NAME builtin, ! etc. Then there is a little text describing ...