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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7
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9k views

Which of these three commands is telling the TRUE Redhat release information

I was checking for the Redhat release so this time I used three different commands. Two commands gave the same result but the third command gave different result. Which one is right. ...
7
votes
1answer
6k views

What does <defunct> mean in the output of ps?

I had issued the ps -ef|grep java command and this is one of the entries that I got : subhrcho 875 803 0 Jan23 pts/5 00:02:27 [java] <defunct> What is <defunct> implying here ? ...
7
votes
2answers
734 views

what is the meaning of this sed command: `;/@/{h;s/test/next/g;x;G}`?

sed -e 's/72;/72, next_val = 0x11111111;/;/@/{h;s/test/next/g;x;G}' fmt_vuln.c > fmt_vuln2.c could you tell me about what is the meaning of ;/@/{h;s/test/next/g;x;G}?
7
votes
2answers
2k 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 ...
6
votes
4answers
3k views

In UNIX, how to find the most commonly used commands in history of unix?

In UNIX, how to find the most commonly used commands in history?
6
votes
3answers
6k 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
6
votes
1answer
498 views

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

I want to know what exactly are Linux commands? & how to identify and locate them? In other words what are different kind/type/category of commands? How to identify them and locate (source) it.
6
votes
2answers
7k views

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
6
votes
2answers
100 views

What does “is hashed” mean when using the type command? [duplicate]

I was reading this post and trying out all of the commands in the first answer... I don't really have anything else better to do right now. Anyways, I ran through them all in regards to rm. What ...
5
votes
4answers
3k 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 ...
5
votes
3answers
6k views

How to permanently enable scl CentOS 6.4?

I installed a newer version of devtoolset (1.1) and was wondering how I would go about permanently setting these to be default. Right now, when I ssh into my server running CentOS, I have to run this ...
5
votes
2answers
922 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: ...
5
votes
3answers
1k views

Linux Rename File Beginning with “--” [duplicate]

Possible Duplicate: How do I delete a file whose name begins with “-” (hyphen a.k.a. dash or minus)? This is an awkward one, I have received some files from a windows machine ...
5
votes
3answers
7k views

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 ...
5
votes
3answers
1k 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.
5
votes
2answers
14k views

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 ...
5
votes
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 ...
5
votes
2answers
468 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 ...
5
votes
1answer
4k 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 ...
5
votes
2answers
1k 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 ...
5
votes
3answers
975 views

Get a list of 3 letter commands on Mac OS X

How can I either create or find a list of 3-letter unix commands on Mac OS X? I'd like to create a new program/command for a project. I'd like to make it a 3-letter name, but I don't want to conflict ...
5
votes
2answers
80 views

how do I call git commands without 'git ' in front?

How do I tell my zsh to automatically try a command with git in front, if the command is not found? E.g. I want to run $ status and if there is no status in $PATH, my zsh should try git status.
5
votes
1answer
469 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 ...
5
votes
2answers
2k 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 ...
5
votes
1answer
1k 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 ...
5
votes
1answer
1k views

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 ...
4
votes
6answers
388 views

Is there a Unix command to quote input lines?

I am wondering if there is a filter command to quote input lines. So when piping: line number 1 line number 2 line number 3 to it, you get: "line number 1" "line number 2" "line number 3" I ...
4
votes
1answer
704 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 ...
4
votes
5answers
338 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?
4
votes
2answers
26k views

Please explain this output of ps -ef command?

A part of the output from the ps -ef command is given below : UID PID PPID C STIME TTY TIME CMD root 1 0 0 2012 ? 00:00:01 init [3] root 2 ...
4
votes
5answers
113 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 ...
4
votes
3answers
2k views

How do I get the list of exit codes (and/or return codes) and meaning for a command/utility?

Is there a way I can do what stated in the title from the terminal commands, or will I have to look into the codes?
4
votes
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}' ...
4
votes
3answers
5k 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 ...
4
votes
1answer
139 views

How to join series of file together side by side without seeing any gap between columns in output?

How can I join several files together in way that there not be any gap between columns in final out put? as an example if following be two inputs: input1.txt 22211 21111 11111 22222 22222 11111 ...
4
votes
1answer
2k 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
3answers
6k 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): ...
4
votes
3answers
5k views

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 ...
4
votes
1answer
101 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 ...
4
votes
2answers
8k 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 ...
4
votes
4answers
1k 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 ...
4
votes
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 ...
4
votes
1answer
120 views

How to execute as the logged-in user in a sudo script (OSX)?

Is there a way to switch contexts like that? The script in my specific case is an installer postinstall script, which requires sudo privileges only for some of the tasks and requires the logged-in ...
4
votes
1answer
241 views

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

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)
4
votes
2answers
462 views

Convert all non-JPG images to JPGs

What command can I use to convert all images in a folder which are not JPGs (PNG and BMP primarily) to JPG? I'd also like the conversion quality to be 100%. And I'd like the converted images to ...
4
votes
3answers
40 views

No command 'bla' found, did you mean:?

So, when a command is not found, by what means is the "did you mean:" list populated? What program finds these alternate commands? What is the meaning of: "(main), (universe)..."? Can I change which ...
4
votes
3answers
325 views

When to use XPG* version of a command?

I occasionally do work on an older Solaris machine whose default version of grep is non-POSIX-compliant. This causes problems in my rc files because the default grep on the machine doesn't support ...
3
votes
5answers
216 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 ...
3
votes
3answers
15k views

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 ?
3
votes
1answer
28k 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 ...