Questions tagged [command-line]

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

Filter by
Sorted by
Tagged with
1042
votes
16answers
2.4m views

How do I get the size of a directory on the command line?

I tried to obtain the size of a directory (containing directories and sub directories) by using the ls command with option l. It seems to work for files (ls -l file name), but if I try to get the size ...
534
votes
9answers
2.0m views

How do I zip/unzip on the unix command line?

How can I create and extract zip archives from the command line?
524
votes
37answers
550k 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 ...
476
votes
4answers
1.4m 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.
473
votes
25answers
481k 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 ...
452
votes
4answers
159k 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 -- in there?
400
votes
9answers
161k views

When should I not kill -9 a process?

I am always very hesitant to run kill -9, but I see other admins do it almost routinely. I figure there is probably a sensible middle ground, so: When and why should kill -9 be used? When and why ...
341
votes
10answers
139k 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 ...
307
votes
11answers
386k views

How can I run a command which will survive terminal close?

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 such ...
293
votes
16answers
351k 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 ...
274
votes
9answers
156k views

How can I find broken symlinks

Is there a way to find all symbolic links that don't point anywere? find ./ -type l will give me all symbolic links, but makes no distinction between links that go somewhere and links that don't. ...
264
votes
6answers
26k 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 ...
260
votes
19answers
180k 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 setup ...
236
votes
24answers
602k 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 ...
229
votes
9answers
860k views

How can I pass a command line argument into a shell script?

I know that shell scripts just run commands as if they were executed in at the command prompt. I'd like to be able to run shell scripts as if they were functions... That is, taking an input value or ...
207
votes
3answers
242k views

How to tell gzip to keep original file?

I would like to compress a text file using gzip command line tool while keeping the original file. By default running the following command gzip file.txt results in modifying this file and renaming ...
206
votes
8answers
159k 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 ...
204
votes
4answers
161k views

What are the differences between most, more and less?

I'm now using Arch Linux, and find a command most works like more and less. To understand the differences between them is a confusing problem. The question Isn't less just more? mentions the ...
195
votes
7answers
203k views

How to remove a single line from history?

I'm working in Mac OSX, so I guess I'm using bash...? Sometimes I enter something that I don't want to be remembered in the history. How do I remove it?
195
votes
18answers
183k 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 /...
191
votes
8answers
515k views

How to terminate a background process?

I have started a wget on remote machine in background using &. Suddenly it stops downloading. I want to terminate its process, then re-run the command. How can I terminate it? I haven't closed ...
188
votes
17answers
501k views

How can I get a count of files in a directory using the command line?

I have a directory with a large number of files. I don't see a ls switch to provide the count. Is there some command line magic to get a count of files?
179
votes
8answers
128k 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 ...
176
votes
11answers
256k views

How do I convert an epoch timestamp to a human readable format on the cli?

How do I convert an epoch timestamp to a human readable format on the cli? I think there's a way to do it with date but the syntax eludes me (other ways welcome).
169
votes
10answers
298k views

How do I make my pc speaker beep

Using bash, how can I make the pc speaker beep? Something like echo 'beepsound' > /dev/pcspkr would be nice.
168
votes
5answers
35k views

I deleted /bin/rm. How do I recover it?

Just for fun, I thought I would use this command on my Raspberry Pi running Raspbian: sudo rm -f /bin/rm I thought I could just reinstall coreutils: I was wrong! apt-get install --reinstall ...
163
votes
4answers
127k views

Find out current working directory of a running process?

What command(s) can one use to find out the current working directory (CWD) of a running process? These would be commands you could use externally from the process.
162
votes
11answers
198k views

How can I edit multiple files in VIM?

I know I can open multiple files with vim by doing something like vim 2011-12*.log, but how can I switch between files and close the files one at a time? Also, how can I tell the file name of the ...
158
votes
4answers
197k views

What is the meaning of IFS=$'\n' in bash scripting?

At the beginning of a bash shell script is the following line: IFS=$'\n' What is the meaning behind this collection of symbols?
157
votes
16answers
231k views

Efficiently delete large directory containing thousands of files

We have an issue with a folder becoming unwieldy with hundreds of thousands of tiny files. There are so many files that performing rm -rf returns an error and instead what we need to do is something ...
152
votes
8answers
265k views

ssh-add complains: Could not open a connection to your authentication agent

I've been trying to get ssh-add working on a RaspberryPi running Raspbian. I can start ssh-agent, when I do it gives the following output into the terminal: SSH_AUTH_SOCK=/tmp/ssh-06TcpPflMg58/...
151
votes
7answers
380k views

How to overwrite target files with mv?

I have a ton of files and dirs in a subdirectory I want to move to the parent directory. There are already some files and dirs in the target directory which need to be overwritten. Files that are only ...
149
votes
22answers
127k views

Markdown Viewer

I found a file formatted with Markdown. Could you guys suggest what viewer that I could use to view this type of files? Hopefully one without gui (if it's possible) Update I was actually looking for ...
147
votes
10answers
58k 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.
143
votes
8answers
512k 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 (...
142
votes
2answers
169k views

How to suspend and resume processes

In the bash terminal I can hit Control+Z to suspend any running process... then I can type fg to resume the process. Is it possible to suspend a process if I only have it's PID? And if so, what ...
141
votes
2answers
613k views

Unzipping a .gz file without removing the gzipped file [duplicate]

I have a file file.gz, when I try to unzip this file by using gunzip file.gz, it unzipped the file but only contains extracted and removes the file.gz file. How can I unzip by keeping both unzipped ...
136
votes
7answers
142k 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?
134
votes
3answers
232k 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....
133
votes
6answers
58k views

When is xargs needed?

The xargs command always confuses me. Is there a general rule for it? Consider the two examples below: $ \ls | grep Cases | less prints the files that match 'Cases', but changing the command to ...
130
votes
6answers
108k views

How to redirect output of wget as input to unzip?

I have to download a file from this link. The file download is a zip file which I will have to unzip in the current folder. Normally, I would download it first, then run the unzip command. $ wget ...
129
votes
1answer
94k views

What is the difference between modify and change in stat command context?

The stat command's manual page says: %x Time of last access %y Time of last modification %z Time of last change I cannot understand the difference between modify and change. I ...
125
votes
8answers
677k views

How can I display the contents of a text file on the command line?

I would like to display the contents of a text file on the command line. The file only contains 5-6 characters. Is there an easy way to do this?
122
votes
6answers
124k views

How do I determine the number of RAM slots in use?

I forgot how many RAM modules are installed on my laptop. I do not want to unscrew it but want to look it up on the console using bash. How do I gather this information?
120
votes
19answers
141k views

Simple command line HTTP server

I have a script which generates a daily report which I want to serve to the so called general public. The problem is I don't want to add to my headaches maintance of a HTTP server (e.g. Apache) with ...
119
votes
36answers
56k views

Quick directory navigation in the bash shell

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 /[full-path]/...
116
votes
12answers
126k 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.
115
votes
13answers
97k 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, )...
111
votes
4answers
99k views

What does <<< mean? [duplicate]

What does <<< mean? Here is an example: $ sed 's/a/b/g' <<< "aaa" bbb Is it something general that works with more Linux commands? It looks like it's feeding the sed program with ...
111
votes
12answers
62k views

diff within a line

I have some sql dumps that I am looking at the differences between. diff can obviously show me the difference between two lines, but I'm driving myself nuts trying to find which values in the long ...