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

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104
votes
9answers
36k views

How do I delete a file whose name begins with “-” (hyphen a.k.a. dash or minus)?

How do you remove a file whose filename begins with a dash (hyphen or minus) -? I'm ssh'd into a remote OSX server and I have this file in my directory: tohru:~ $ ls -l total 8 -rw-r--r-- 1 me ...
162
votes
16answers
113k views

How to do integer & float calculations, in bash or other languages/frameworks?

Using echo "20+5" literally produces the text "20+5". What command can I use to get the numeric sum, 25 in this case? Also, what's the easiest way to do it just using bash for floating point? For ...
111
votes
7answers
66k views

Keep SSH Sessions running after disconnection

I sometimes have long running processes that I want to kick off before going home, so I create a SSH session to the server to start the process, but then I want to close my laptop and go home and ...
199
votes
5answers
13k views

What's the difference between $(stuff) and `stuff`?

There are two syntaxes for command substitution: with dollar-parentheses and with backticks. Running top -p $(pidof init) and top -p `pidof init` gives the same output. Are these two ways of doing the ...
144
votes
3answers
38k views

What does “--” (double-dash) mean? (also known as “bare double dash”)

I have seen -- used in the compgen command. For example: compgen -W "foo bar baz" -- b What is the meaning of the --.
31
votes
4answers
78k views

Why do we use “./” to execute a file?

Why do we use ./filename to execute a file in linux? Why not just enter it like other commands gcc, ls etc...
127
votes
7answers
106k views

How can I close a terminal without killing the command running in it?

Sometimes I want to start a process and forget about it. If I start it from the command line, like this: redshift I can't close the terminal, or it will kill the process. Can I run a command in ...
9
votes
4answers
44k views

Storing output of command in shell variable [duplicate]

I have an operation using cut that I would like to assign result to a variable var4=echo ztemp.xml |cut -f1 -d '.' I get the error: ztemp.xml is not a command The value of var4 never gets ...
34
votes
13answers
15k views

Is there a robust command line tool for processing csv files?

I work with CSV files and sometimes need to quickly check the contents of a row or column from the command line. In many cases cut, head, tail, and friends will do the job; however, cut cannot easily ...
48
votes
7answers
9k views

Is there a one-liner that allows me to create a directory and move into it at the same time?

I find myself repeating a lot of: mkdir longtitleproject cd longtitleproject Is there a way of doing it in one line without repeating the directory name? I'm on bash here.
35
votes
10answers
23k views

How to understand what's taking up space?

I'm looking for a linux alternative to WinDirStat. I would like to know what is taking up space on my hard drives. A program that works on console and doesn't require a UI is preferred .
79
votes
13answers
51k views

how do you sort du output by size?

How do you sort du -sh /dir/* by size? I read one site that said use | sort -n but that's obviously not right. Here's an example that is wrong. [~]# du -sh /var/* | sort -n 0 /var/mail 1.2M ...
52
votes
4answers
41k views

What is the difference between Halt and Shutdown commands?

What is the difference between the halt and shutdown commands?
12
votes
3answers
957 views

Order of redirections

I don't quite understand how the computer reads this command. cat file1 file2 1> file.txt 2>&1 If I understand, 2>&1 simply redirect Standard Error to Standard Output. By that ...
14
votes
2answers
1k views

Manipulating X key and pointer grabs on the command line

What command line tools exist to list and manage X server grabs? (That's grab as in key and pointer grabs, i.e. restricting the use of a particular key or mouse button to a particular application, or ...
139
votes
17answers
72k views

How to have tail -f show colored output

I'd like to be able to tail the output of a server log file that has messages like: INFO SEVERE etc, and if it's SEVERE, show the line in red; if it's INFO, in green. What kind of alias can I ...
79
votes
30answers
22k views

Quick directory navigation in the terminal

I would like to frequently switch between directories that are in totally unrelated paths, for example /Project/Warnest/docs/ and ~/Dropbox/Projects/ds/test/. But I don't want to type cd ...
10
votes
5answers
1k views

What's the best way to take a segment out of a text file?

What's a good way of extracting say, lines 20 -45 out of a huge text file. Non-interactively of course!
200
votes
32answers
147k views

Tracking down where disk space has gone on Linux?

When administering Linux systems I often find myself struggling to track down the culprit after a partition goes full. I normally use du / | sort -nr but on a large filesystem this takes a long time ...
62
votes
9answers
40k views

How can I move files and view the progress (e.g. with a progress bar)?

When moving large directories using mv, is there a way to view the progress (%)? The cp command on gentoo had a -g switch that showed the progress.
66
votes
5answers
47k views

How can I send stdout to multiple commands?

There are some commands which filter or act on input, and then pass it along as output, I think usually to stdout - but some commands will just take the stdin and do whatever they do with it, and ...
68
votes
9answers
3k views

Remember a half-typed command while I check something

I often find myself in the following position: I've started typing a long command at the bash prompt, but half-way through I find out I need to check something with another command. This is a problem ...
68
votes
12answers
34k views

How to grep a specific line _and_ the first line of a file?

Assuming a simple grep such as: $ psa aux | grep someApp 1000 11634 51.2 0.1 32824 9112 pts/1 SN+ 13:24 7:49 someApp This provides much information, but as the first line of the ps ...
43
votes
9answers
10k views

Linux tools to treat files as sets and perform set operations on them

Does anyone know of any linux tool specifically designed to treat files as sets and perform set operations on them? Like difference, intersection, etc?
49
votes
11answers
28k views

Easy way to determine virtualization technology

I have command line access to a Linux machine which may or may not be virtualized. I want to determine what kind of virtualization technology it runs on, if any (VMWare, VirtualBox, KVM, OpenVZ, Xen, ...
44
votes
4answers
44k views

Understanding the exclamation mark (!) in bash

I used history | less to get the lines of previous commands and from the numbers on the left hand side I found the line I wanted repeated (eg. 22) and did !22 at the command prompt and it ...
29
votes
4answers
8k views

Single dashes `-` for single-character options, but double dashes `--` for words?

Where did the convention of using single dashes for letters and doubles dashes for words come from and why is continued to be used? For example if I type in ls --help, you see: -a, --all ...
23
votes
7answers
6k views

how to glob every hidden file except current and parent directory [duplicate]

I want to glob every hidden file and directory, but not the current (.) and parent directory (..). I am using bash. Observe current behaviour: $ ls -a . .. ...a ...aa ..a ..aa .a .aa .aaa ...
10
votes
2answers
4k views

Find filesystem of an unmounted partition from a script

I'm writing a custom automated install using AIF (Arch Installation Framework), and I need to find the filesystem on a partition given a partition. So far I have this: grok_partitions () { local ...
12
votes
1answer
3k views

What does *~ mean?

At the end of a makefile I saw rm -f *~ *.class I understand the *.class, but what's *~?
221
votes
23answers
158k views

Repeat a Unix command every x seconds forever

There's a built-in Unix command repeat whose first argument is the number of times to repeat a command, where the command (with any arguments) is specified by the remaining arguments to repeat. For ...
42
votes
7answers
122k views

Run a command without making me wait

On the CLI, sometimes a command I type takes a while to complete, and sometimes I know when that's about to happen. I'm a bit confused on "backgrounding" and such in Linux. What is the most common ...
25
votes
9answers
2k views

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

Is there a command to tell what type of filesystem you're using?
21
votes
5answers
40k views

How can I make a program executable from everywhere

What should I do if I want to be able to run a given program regardless of my current directory? Should I create a symbolic link to the program in the /bin folder?
7
votes
6answers
1k views

How can I reproduce commands run on one machine on another machine?

I would like to install some software on a linux-machine that I have run in VirtualBox. Then I would like to do the same thing on a linux-VPS. I think that I can save all commands that I run using ...
9
votes
1answer
2k views

How to run my own program without specifying its path

Let's suppose I have compiled something and I run it like so: $ /path/to/my/executable/mycmd Hello World What do I need to do to run it like $ mycmd Hello World from everywhere in my computer? ...
27
votes
5answers
7k views

How do I send stdin to the clipboard?

Is there functionality in unix that allows for the following: echo "Some Text" | copy-to-clipboard
20
votes
5answers
6k views

Why is echo a shell built in command?

$ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons?
12
votes
5answers
9k views

Make cd automatically ls

I find that I often do the following: %> cd bla/bla %> ls I would like it that whenever I cd into a directory it automatically does an ls. I fiddled with my .bashrc for a while, but couldn't ...
8
votes
4answers
533 views

ls command operating differently depending on recipient

How does commands like ls know what its stdout is? It seems ls is operating different depending on what the target stdout is. For example if I do: ls /home/matt/tmp the result is: a.txt b.txt ...
40
votes
6answers
22k views

Split pages in pdf

I have a scanned pdf file which has scanned two pages on one virtual page (page in pdf file). The resolution is with good quality. The problem is I have to zoom when reading and drag from left to the ...
42
votes
4answers
55k views

How to copy the partition layout of a whole disk using standard tools

I want to take a backup of the whole partition layout of a hard drive, including logical drives, so that I can restore that layout to another disk. I do not want to copy the contents of the ...
39
votes
11answers
20k views

How do I reuse the last output from the command line?

This is a noob question, but I'd like to know how to reuse the last output from the console, ie: pv-3:method Xavier$ python -c "from distutils.sysconfig import get_python_lib; print get_python_lib()" ...
39
votes
6answers
67k views

Where do files go when the rm command is issued?

Recently I accidentally did rm on a set of files and it got me thinking where exactly these files end up? That is to say, when working with a GUI, deleted files go to the Trash. What's the equivalent ...
13
votes
8answers
25k views

Is there a simple linux command that will tell me what my display manager is?

Is there a simple linux command that will tell me what my display manager is? I'm using Xfce. Are different desktop environments usually affiliated with different display managers?
38
votes
10answers
32k views

Which mp3 tagging tool for Linux?

Which app would you recommend for Linux to tag MP3s? Under Windows I used to use tag&rename and liked it a lot; it works well under Wine, but I want something that runs natively
30
votes
8answers
66k views

Do we have an undo in Linux?

I renamed a few files in one batch script. Is there a way to undo the changes without having to rename them back? Does Linux provide some native way of undoing?
16
votes
5answers
49k views

Pass the output of previous command to next as an argument

I've a command that outputs data to stdout (command1 -p=aaa -v=bbb -i=4). The output line can have the following value: rate (10%) - name: value - 10Kbps I want to grep that output in order to ...
11
votes
2answers
3k views

When do su and sudo use different passwords?

I am able to run anything using sudo; my password is accepted. But whenever I try to do su from a shell, it fails with: su: incorrect password What can the problem be?
22
votes
2answers
2k views

Is there a reason why ls does not have a --zero or -0 option

This question was prompted by questions about ls' -1 option and the recurring tendency of people to ask question and answers that includes processing the output of ls. This reuse of the output ls ...