One or a set of directives issued in the *nix environment to get information, change the state of something or to execute something. In other words: To gain an objective.

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Why doesn't ln -s tell that it fails when creating a symlink to an existing symlinked directory?

When running (on linux different ubuntu variations): >ln -s dir_1 symlink_dir >ln -s dir_2 symlink_dir It fails without telling that it fails. But if you do the same thing on a file instead ...
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4answers
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How to randomly sample a subset of a file

Is there any Linux command one can use to sample subset of a file? For instance, a file contains one million lines, and we want to randomly sample only one thousand lines from that file. For random ...
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1answer
436 views

What exactly are commands? How to identify? [duplicate]

I want to know what exactly are Linux commands? & how to identify and locate them? (Say Introduce the "commands") In other words what are different kind/type/category of commands? How to identify ...
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3answers
4k views

Test command in unix doesn't print an output

When I type this in the terminal test 4 -lt 6 I don't get any output. Why not? I need that 0 or 1
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2answers
393 views

Get the actions for a command programmatically

Let's take the git example: $ git<TAB><TAB> git git-import-dscs git-shell git-buildpackage git-import-orig git-upload-archive git-dch git-pbuilder ...
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4answers
882 views

Is there a practical use for the GNU factor command?

Looking through the GNU Coreutils, I spotted the factor command, that I had never noticed before. Reading the man page: Print the prime factors of each specified integer NUMBER. If none are ...
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votes
1answer
3k views

What is the use of literal command in ftp?

Browsing through FTP help (i.e. ftp> ?), showed me a command name literal, description of which is ftp> ? literal literal Send arbitrary ftp command I tried to do some trial and ...
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2answers
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How to execute one command on all files within a folder

Saying, I have this tree and I want to execute ruby on all scripts within the folder. How could I archive through one line of command. ./ ../ rb-script/ sample1.rb sample2.rb
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2answers
641 views

Why is cd not a file in /bin? [duplicate]

Possible Duplicate: Why is cd not a program? I noticed that every other commonly used util, like ls, cp, rm, etc. are actually files in /bin -- but cd is not. Nor is it in any other ...
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1answer
1k views

Git auto-complete

I am using Git as many of you do. Also, I don't use any GUI for that — just CLI. So I was wondering: are there any way to make Git commands (git status, git checkout etc.) complete themselves when ...
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1answer
337 views

What does `init [2]` mean in the COMMAND column of ps?

Reading What do the brackets around processes mean? I understand that the executable name is printed. Linux ps man page: Sometimes the process args will be unavailable; when this happens, ps will ...
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1answer
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Command & binary exists but cannot be executed

I transfered /etc/* files from one Linux server to another and now I have a strange error. Both are Debian Squeeze. When I run a command, e.g. ssh, I get an error: bash: /usr/bin/ssh: No such file ...
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72 views

Merging/Combining 2 text files according to numeric field

I have 2 text files file_1: 14595|Age 35|Salary xx|Position ax|2013|Info 1|Info 2|Info 3|Info 4|Info 5 14649|Age 30|Salary xx|Position az|2015|Info 1|Info 2|Info 3|Info 4|Info 5 file_2: ...
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votes
1answer
596 views

Which 2-letter POSIX command is different from all the others?

I was interviewed for an internship and I got the same question as this one: http://www.glassdoor.com/Interview/Which-2-letter-POSIX-command-is-different-from-all-the-others-QTN_498236.htm The ...
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votes
4answers
1k 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 ...
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5answers
301 views

Showing all pages at once with man command [duplicate]

Say if I run the command man who, I have to keep pressing space or enter to show all content. Is there a way to show all of the content at once?
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5answers
108 views

unix command to print till 3rd occurence of “/” in each line

I have one file contains data as follows... /tutordashboard/manageTutorLogInStatus/?ua=TQ-AUTOCLOSE-REENTER&filterId=089089087087080&dt=1325757272 ...
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votes
2answers
722 views

Command completion does not complete the files in the current directory

Something is wrong with my tab completion. Let's say I do this: cd test // works fine, go into test directory ls // works fine, displays all of the files Let's assume I have the following files: ...
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votes
2answers
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print command instead of echo in linux

I simply can print a message in terminal using linux echo command. prayag@prayag$ echo "prayag works on JVM" prayag works on JVM Can I have the same output with print command. I actually went ...
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3answers
323 views

Get last part of string after hyphen

Is there a simple command line to extract the last part of a string separated by hyphens? E.g., I want to extract 123 from foo-bar-123.
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5answers
2k views

Execute string result from shell script as a set of shell commands

I create a string result from my shell script and i want to execute it as a shell command. For example file_a is: user1@gmail.com user2@gmail.com script: awk '{print "mail -s \"welcome\"", $1}' ...
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votes
1answer
533 views

ZIP files with size limit

Is there a command to create multiple ZIP files based on file size? So that in a folder of 600 files, totalling 1 GB, the command will create 4 zips roughly equal to 250mb. There's a similar command ...
4
votes
1answer
77 views

How to update 'command cache' after change of soft links?

I have changed multiple soft links on my system with ln -f -s. When I view the link with ls -l, I see they point to the right target. However, when I try to run the command, it still tries to use the ...
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2answers
1k views

Memory usage command with syntax similar to the time command

What command shows the memory usage of a program, i am looking for a command that is simple to use and has similar syntax to the time command. I am trying to find the memory usage of a md5 hashing ...
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votes
3answers
4k views

Split command output by linebreak?

I have a command returning multiple lines. For further processing I need to process each single line of those lines. My current code works by modifying the IFS (Internal Field Separator): ...
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3answers
2k views

How to find a file with specific permission of a specific user?

How do I get a list of all the files which permission is "read and write" for a specific user. For example, when I go on the desktop of my mac, then right click on file "A", then "get info", then on ...
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votes
2answers
6k views

How to see the total progress while copying the files

We know that if we give --progress parameter to rsync it will show the progress of files copied. But issue is that is shows the progress for each single file not total or overall progress. So how to ...
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votes
2answers
1k views

How to use getopt in bash command line with only long options?

There is a getopt command in bash command line. getopt can used with short options (such as getopt -o axby "$@"), and can be used with both short and long options (such as getopt -o axby -l long-key ...
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votes
1answer
860 views

What is the difference between exiting a process via Ctrl+C vs issuing a kill -9 command?

I know I can kill any process with kill -9 command . But sometimes i see that even if I have terminated a program with CTRL+C , the process doesn't get killed . So I want to know the difference ...
4
votes
1answer
207 views

What does the command “$()” do in UNIX?

What does the command $() do in UNIX? Could someone explain what is the significance of $ in the below examples; $(echo var=10) and eval $(echo var=10)
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votes
5answers
212 views

find which system is transmitting through a particular port

I am using command nc -lu <port no.> to find on given port any data is receiving or not. I am getting data if there is transmission going on (but don't know from where!). Is there any way that ...
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3answers
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What is the difference between ps and top command?

What is the difference between ps and top command ? I see that both can display information about running processes . Which one should be used when ?
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2answers
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Redhat Linux: How to know my system configuration?

I am using Red Hat Enterprise Linux Server release 5.9 (Tikanga). For installation of any application, it is very important to know the system configuration, is it 32 bit or 64 bit system, Installed ...
3
votes
1answer
23k views

Does Linux allow executing the “rm -rf / ” command? [closed]

We all know that we have to use the -rf option of rm command carefully. What I wonder is does Linux allow executing this command: rm -rf /? If so, why? This command could have disastrous ...
3
votes
3answers
907 views

Shortening build command

Is there any way I can shorten this openCV build command? g++ file.cpp -o newFileName `pkg-config --cflags --libs opencv` I tried adding: -o newFileName `pkg-config --cflags --libs opencv` to an ...
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votes
3answers
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How to list available app commands in terminal

I'm using fluxbox and recently i wanted to start an application for video editing and i couldn't remember it's name. I usually run apps from terminal so I was wondering is there a way to list all ...
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2answers
165 views

What filesystem mount point am I currently working on?

I would like to know in what filesystem mount point I am currently on, similarly to using pwd to know what directory I am in. I know you can use df . (or df $(pwd) or many variants), but I find it ...
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votes
2answers
3k views

How can I restore file timestamps of video recordings using the embedded metadata?

I'm looking for a command that will read the metadata of a ‘*.mp4’ file and touch the file's timestamp with the creation time of the video. The command should be read-only with respect to the file ...
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votes
4answers
939 views

What are commands to find shell keywords, built in functions and user defined functions?

I was discussing with my friend on how the commands are parsed in the shell, and he told me that bash searches the command in following order List of aliases List of shell keywords List of ...
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votes
1answer
1k views

Searching a file & excluding lines with a specified string

I have a large log file that contains numerous lines of the same entry, lets call it "repeat-info". As an example here is what a portion of the log might look like: [Timestamp] repeat-info ...
3
votes
3answers
61 views

Quick change directory to a similar directory structure?

In the test environment, we have a directory structure for log files that looks like this: /var/Logs/int/app-id/region-code/log/file-name.log /var/Logs/sat/app-id/region-code/log/file-name.log ...
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votes
2answers
76 views

What is the name of the app displaying custom text in fullscreen size?

I have seen years ago a very handy application: the command displayed it's first argument enlarged to fit the whole screen. For example... thiscommand AA ...then you could see two very big A ...
3
votes
1answer
221 views

command not found handle doesn't work for url

I'm trying to setup the command_not_found_handle for URL links, %> command_not_found_handle() { echo "OK"; } %> aaaaa OK %> http://www.google.com bash: http://www.google.com: No such file or ...
3
votes
2answers
621 views

Please explain the -f option in pgrep

man pgrep says the following about -f option: -f The pattern is normally only matched against the process name. When -f is set, the full command line is used. What does it ...
3
votes
2answers
460 views

Make copies of a single directory to multiple directories with different names

I'm trying to replicate a single directory (with sub-directories) to a bunch of new directories based on a list. For example I can: mkdir Fred Barney Thelma Louise Foo Bar How would I copy a premade ...
3
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1answer
42 views

Switching users without the - symbol

I had to switch to a different user earlier for something that I was working on. I have originally done: su support While I was successfully able to switch to support, I found I was unable to make ...
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votes
1answer
2k views

How can I pipe commands to any terminal?

I often use more than one terminal (or terminal emulator) at a time; and while in X I can copy-paste commands, besides not being very practical, it obviously does not work on the real TTY. The first ...
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votes
3answers
793 views

Correctly parse arguments in script behaving like a shell called through SSH

I have a server with a very limited used whom I want to be able to run two very specific (and custom) instructions through SSH. In order to do that, I have set the shell for that limited user to be a ...
3
votes
2answers
891 views

is there any command like “wall” that runs a “command” in all terminals

as you know "wall" command sends a message to all terminals: wall message now my question is this: is there any command that can send a "command" to be run in all terminals? for example sending ...
3
votes
1answer
2k views

Make awk use bash with the system() command

Is there a way to make awk use bash instead of sh when running system commands using the system() call? I want to use some bash-specific features such as [[ ]] and < > string comparison operators: ...