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

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Why is bash's prompt variable called PS1?

The environment variable for the bash prompt is called PS1 (usually set in ~/.bashrc). What does PS1 stand for? Is there a PS2?
28
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3answers
22k 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 ...
28
votes
6answers
44k 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 ...
28
votes
4answers
7k views

How can I display syntax highlighting on a file?

Is there a variant of cat that outputs syntax-highlighted lines of code when used on a source file? An idea: maybe vi[m] or another editor can be asked to dump the syntax-highlighted contents of said ...
28
votes
7answers
12k views

Converting colored output into html

There are tools providing coloured output: dwdiff -c File1 File2 # word level diff grep --color=always # we all know this guy ... The question is: How to convert their colored output of arbitrary ...
27
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2answers
94k 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 ...
27
votes
2answers
51k views

How to use command line to change volume?

I am trying to control the volume using my programming script. How can I do the following in Fedora 15, Ubuntu linux? Mute/ Unmute Volume up and volume down Note: Please note that I use a web USB ...
27
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2answers
30k views

How to grep the output of cURL?

I need to retrieve the expiry date of an SSL cert. The curl application does provide this information: $ curl -v https://google.com/ * Hostname was NOT found in DNS cache * Trying 212.179.180.121......
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4answers
150k views

Connecting to wifi network through command line

I am trying to connect to my WEP network just using the command-line (Linux). I run: sudo iwconfig wlan0 mode Managed essid 'my_network' key 'xx:xx:... hex key, 26 digits' Then I try to obtain an ...
27
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5answers
55k 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?
27
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4answers
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How to Execute multiple command using nohup

I need to execute multiple commands using nohup. Each command should be executed after the previous command. I used this command as an example: nohup wget $url && wget $url2 > /dev/null ...
26
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8answers
2k views

Dealing with file names with special first characters (ex. ♫)

I have recently come across a file whose name begins with the character '♫'. I wanted to copy this file, feed it into ffmpeg, and reference it in various other ways in the terminal. I usually auto-...
26
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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?
26
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5answers
29k 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 ...
26
votes
2answers
5k views

disable CTRL-D window close in terminator (terminal emulator)

I am often logged in through multiple SSH sessions. To logout from my sessions, I press CTRL+d, until I am back on my local machine. However, sometimes I press once too many, and my terminal exits. ...
26
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4answers
4k 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 ...
26
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2answers
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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 ...
25
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4answers
4k views

Is it possible to define a command in bash?

For example, can I set gb = cd /media/Dan/evolution So that everytime I execute gb in bash, I can cd to that particular directory? I find something online, alias command. But It seems can't do the ...
25
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4answers
18k 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 ...
25
votes
1answer
48k views

Using --exclude with the du command

This is probably something basic but I'm not able to make it work. I'm trying to use DU to get a total size of files minus certain directories. I need to exclude one specific directory called uploads ...
24
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10answers
5k views

Run two commands on one argument (without scripting)

How can I perform two commands on one input, without typing that input twice? For example, the stat command tells a lot about a file, but doesn't indicate its file type: stat fileName The file ...
24
votes
6answers
50k 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?
24
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2answers
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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 ...
24
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3answers
11k views

Use & (ampersand) in single line bash loop

I have been using this command successfully, which changes a variable in a config file then executes a Python script within a loop: for((i=114;i<=255;i+=1)); do echo $i > numbers.txt;python ...
24
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6answers
30k views

How do I limit the number of files printed by ls?

Is there a way to limit the quantity of listed files on a ls command? I've seen: ls | head -4 but to get head or tail to be executed I need to wait for ls to finish execution, and with directories ...
24
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1answer
71k views

How do I get sar to show for the previous day?

on our servers, typing sar show's the system load statistics for today starting at midnight, is it possible to show yesterdays statistics?
24
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4answers
22k views

What is the purpose of the 'install' command?

I've seen the install command used in a lot of Makefiles, and its existence and usage are kind of confusing. From the manpages, it seems like a knockoff of cp with less features, but I assume it ...
23
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2answers
3k 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?
23
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3answers
2k views

How can I shutdown a RHEL server at 06:45 tomorrow morning?

I just received notification that our site has a power outage tomorrow morning. I am a Windows admin but I have to cover for our Linux admin who's not around until tomorrow evening. I need to ...
23
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4answers
51k views

Grabbing the first [x] characters for a string from a pipe

If I have really long output from a command (single line) but I know I only want the first [x] (let's say 8) characters of the output, what's the easiest way to get that? There aren't any delimiters.
23
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14answers
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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 that'...
23
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2answers
2k 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" ...
23
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5answers
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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 ...
23
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2answers
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How can I verify SSL certificates on the command line?

I'm trying to validate/verify that the rsa key, ca-bundle, and certificate stored here are ok. They are not being served by a webserver. How can I verify them?
23
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2answers
9k views

What is meant by a shell is in “vi” mode or “emacs” mode?

This question follows directly from the answer. In this case I am specifically unable to understand the part which says: In that regard, its behaviour is closer to emacs' than with bash(readline)...
23
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1answer
2k 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 ...
23
votes
7answers
5k 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 ...
22
votes
4answers
35k views

How do I make multiple directories at once in a directory?

I know with mkdir I can do mkdir A B C D E F to create each directory. How do I create directories A-Z or 1-100 with out typing in each letter or number?
22
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8answers
1k views

Clipboard for copying and pasting files in command line?

In Bash, suppose I visit a directory, and then another directory. I would like to copy a file from the first directory to the second directory, but without specifying the long pathnames of them. Is it ...
22
votes
9answers
44k views

Generate random numbers in specific range

After googling a bit I couldn't find a simple way to use a shell command to generate a random decimal integer number included in a specific range, that is between a minimum and a maximum. I read ...
22
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3answers
14k 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 ...
22
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4answers
1k views

Are Linux utilities smart when running piped commands?

I was just running a few commands in a terminal and I started wondering, does Unix/Linux take shortcuts when running piped commands? For example, let's say I have a file with one million lines, the ...
22
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11answers
97k views

List of useful `less` functions

Rather than ask for your favorite, lets just list them off. What are the more useful commands inside less? Personally, I use: / (search forward) ? (search backwards) F (enable tail -f like ...
22
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5answers
8k views

How can I remove duplicates in my .bash_history, preserving order?

I really enjoying using control+r to recursively search my command history. I've found a few good options I like to use with it: # ignore duplicate commands, ignore commands starting with a space ...
22
votes
3answers
32k views

Sort and count number of occurrence of lines

I have Apache logfile, access.log, how to count number of line occurrence in that file? for example the result of cut -f 7 -d ' ' | cut -d '?' -f 1 | tr '[:upper:]' '[:lower:]' is a.php b.php a.php c....
22
votes
8answers
10k 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 ...
22
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3answers
21k views

Generate File of a certain size?

I'd like to generate a file with the name example.file. I could use touch example.file but I want the file to be exactly 24MB in size. I already checked the manpage of touch, but there is no ...
22
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4answers
17k views

Count number of lines of output from previous program

I'm trying to count the number of lines of output a certain program produces. The problem is, the program takes a long time to run, and I want to display the output to the user. Is there a way to ...
21
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5answers
7k 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?
21
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6answers
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How to output only file names (with spaces) in ls -Al?

I should echo only names of files or directories with this construction: ls -Al | while read string do ... done ls -Al output : drwxr-xr-x 12 s162103 studs 12 march 28 12:49 personal ...