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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93
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7answers
10k views

Why is cd not a program?

I've always wondered why cd isn't a program, but never managed to find the answer. Anyone know why this is the case?
41
votes
2answers
2k views

What is the point of the `cd` external command?

As referenced in this fine answer, POSIX systems have an external binary cd in addition to the shell builtin. On OS X 10.8 it's /usr/bin/cd. You can't use it like the builtin cd since it exits ...
47
votes
3answers
20k views

How to stop the find command after first match?

Is there a way to force the find command to stop right after finding the first match?
25
votes
3answers
5k views

What does “rm is hashed” mean?

I'm going through http://mywiki.wooledge.org/BashGuide/CommandsAndArguments and came across this: $ type rm rm is hashed (/bin/rm) $ type cd cd is a shell builtin Just a little earlier, the guide ...
5
votes
1answer
466 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 ...
3
votes
3answers
301 views

What is $() in a command?

What is $() in Linux Shell Commands? For example: chmod 777 $(pwd)
2
votes
4answers
3k views

List all commands that a shell knows

What can I type at my shell (which happens to be bash) that will list all the commands that are recognized? Also, does this differ by shell? Or do all shells just have a "directory" of commands they ...
73
votes
15answers
14k views

What are the legitimate uses of the `touch` command?

What's the point of the touch command? I know I can create empty files with it, but so is also the case with echo -n. Otherwise, why would someone need to change the timestamps of a file? Unless to ...
13
votes
3answers
11k views

What is the purpose of -e in sed command?

I can't find any documentation about the sed -e switch, for simple replace, do I need it? e.g. sed 's/foo/bar/' VS sed -e 's/foo/bar/'
9
votes
2answers
10k views

Execute command in remote active terminal

Suppose you have a terminal emulator (T1) open with a PID of 6350. From another terminal, type this command (C1): echo "ls\n" > /proc/6350/fd/0 This writes ls and the new line in T1 but does ...
1
vote
2answers
38 views

Is it possible to specify a path in which a directory name is variable?

Asking this question on mpv player and dvds, I stumbled into a more generic question: is it generally possible to specify a path in which one of the directory names is variable? Let's say that I want ...
100
votes
3answers
11k views

Why is “echo” so much faster than “touch”?

I'm trying to update the timestamp to the current time on all of the xml files in my directory (recursively). I'm using Mac OSX 10.8.5. On about 300,000 files, the following echo command takes 10 ...
25
votes
3answers
2k views

Which are the standard commands available in every Linux based distribution?

I would like to know which are the standard commands available in every Linux system. For example if you get a debian/ubuntu/redhat/suse/arch/slackware etc, you will always find there commands like: ...
27
votes
5answers
5k views

The “yes” command

There is a yes command in unix/linux which basically infinitely prints y to the stdout. What is the point of it, and how is it useful?
21
votes
2answers
810 views

What is `--` called?

Recently I got to know of -- that is double-hyphen which is used to tell a command that the option list has ended and what follows should not be considered as a option. So, grep -- 'search_word' * ...
10
votes
2answers
4k views

What's the difference between “dir” and “ls”?

I have compared the man pages of dir and ls and they seem to be exactly the same. Both are part of GNU coreutils and "list directory contents". The only difference I've seen so far is that dir ...
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
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 ...
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
7
votes
2answers
561 views

Order of executables started in bash

If I execute the test command in bash, test(evaluates conditional expression) built-in utility is started: $ type test test is a shell builtin $ type -a test test is a shell builtin test is ...
2
votes
3answers
7k views

Find executable files recursively

I have got the directory called Test and a few directories inside it. Both Test and the directories inside it have executable files. I'd like to print them with ls. I'd use this command. ls -l `find ...
2
votes
3answers
3k views

Why does Firefox refuse to die despite killing it with pkill -9?

I am issuing the following command to kill Firefox on my Red Hat Linux box: [subhrcho@slc04lyo ~]$ pkill -9 -f firefox [subhrcho@slc04lyo ~]$ However, when I try to invoke Firefox through ...
1
vote
2answers
45 views

Does an external command which takes a command as its argument has restriction on the argument?

For an external command which takes a command as its argument, must the argument be an external command, not a shell's builtin command? I ask this question, based on the following two examples the ...
0
votes
0answers
19 views

How to test if a command is installed? [duplicate]

For example, if I'm writing a shell script which: depends completely on a specific command being available/installed, or is intended to make use of a specific command if it is available (and ...
0
votes
1answer
92 views

list users who are all created by current user in linux

I have set of users with root access.I want to know list of users who are all created by currently logged in user. From below structure if user1 login to system , how to list user's like ...
0
votes
2answers
221 views

Why does this compound command report errors when copying directories?

if one executes the following two commands in one line, as follows, rm -rf dir ; cp -r dir2 dir it may complain that cp can not create directory dir/subdir: File exists but if these two commands ...
-3
votes
2answers
46 views

Find and replace in Linux [closed]

I want to replace 0/1 with hetero but whenever I am trying to use the known commands it is showing syntax error because the / is aleady part of the command .. Can anyone suggest a command to solve ...
39
votes
3answers
50k views

find - exec rm vs -delete

I'm trying to understand the difference between these two commands: sudo find / -name .DS_Store -delete and sudo find / -name ".DS_Store" -exec rm {} \; I noticed that the execmethod is ...
19
votes
9answers
36k 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 ...
8
votes
3answers
6k views

Difference between 'ifconfig' and 'ip' commands

I read some articles/tutorials on 'ifconfig' command, most of them included a common statement - "ifconfig is deprecated by ip command" and suggested to learn ip command. But none of them ...
12
votes
5answers
1k views

How to recall a previous command (without execution) in order to change it?

I can't remember the trick where I could get the last command without running it: let's say I want to be be able to access the command !1255 when pressing the up arrow key and modify the command. So ...
0
votes
1answer
217 views

Command not working anymore in Thunar custom actions

I used to create a Thunar custom action as presented here in order to extract audio without transcoding from selected (multiple) video files . The command to be added in Thunar custom actions list ...
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 ...
3
votes
3answers
14k 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 ?
15
votes
1answer
638 views

What does yes $(yes yes) do?

Wondering what use the yes command might be, I stumbled upon this comment, and tried to execute yes $(yes yes) From what I understand, this should simply print out an infinite sequence of yes, but ...
13
votes
4answers
1k views

What is the difference between running a executable just by name and by appending a dot /slash before it?

This is the output from ls -all command : -rwxr----- 1 subhrcho dba 3600 Nov 13 17:26 jdev -rw-r----- 1 subhrcho dba 1566 Nov 13 17:26 jdev-Darwin.conf -rw-r----- 1 subhrcho dba 347 Mar 6 2009 ...
8
votes
4answers
167 views

Is there a tool for summarizing what all commands do?

So I understand that there are man pages for getting the documentation when the internet is unavailable, or when you need advanced uses, but what if I'm offline and I don't even know what tool I need ...
7
votes
2answers
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. ...
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.
3
votes
1answer
2k views

How to check will my computer is going to reboot(or shutting down)?

When I send a reboot command(or shutdown) command to a Linux machine does it keeps that messages at somewhere and can I query it. I.e. I will send a reboot command and after that I will run another ...
0
votes
2answers
388 views

What is the Run prompt equivalency in Linux?

In Windows, there is the Run prompt, which you can access with Win+R key. What is the equivalency to this in Linux? Is there even such a thing or is the Terminal the main prompt you would use in ...
8
votes
0answers
215 views

how to get exit status from the command before the last [duplicate]

I have solaris machine ( solaris 10 ) please Look on the following simple commands (haconf -makerw | grep -iq "Cluster already writable") # haconf -makerw VCS WARNING V-16-1-10364 Cluster ...
3
votes
3answers
321 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
1answer
3k 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 ...
2
votes
1answer
162 views

How to convert .doc to ODF with a command line?

I'd like to convert many Microsoft Word documents to ODF (the OO.org formata with a command line (because there are many of them). (I need them for reading afterwards on a device where reading OO.org ...
1
vote
2answers
218 views

not able to execute multiple commands on multiple linux machines?

I have around 50 ubuntu machines on which I need to run below commands: sudo apt-get install htop sudo scp -r todd@machineA.host.com:/home/todd/pip /tmp/ sudo apt-get install python-pip sudo pip ...
0
votes
2answers
2k views

Why screen is not splitting my GNOME terminal?

I am working in a remote Linux box using VNC.I have a single terminal with lots of tabs opened in my system. How can I split them using the screen utility? Does the screen utility work with already ...