4
votes
1answer
39 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 ...
3
votes
4answers
65 views

Generate random numbers in specific range

After googling a bit I couldn't find a simple way to generate with a shell command a random number included in a specific range, between a minimum and a maximum. I read about /dev/random, ...
5
votes
1answer
79 views

What's the difference between “realpath” and “readlink -f”

I've read a lot about realpath command and how it has been deprecated with the readlink -f being now recommended. I have also seen in some places that the reason why realpath was introduced was for ...
5
votes
2answers
278 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 ...
1
vote
1answer
88 views

`tar` with `find` with removing original file extension

I want to create tb2 files from bunch of text files like this. tar cfj $(basename ./2014_04_09.txt .txt).tb2 $(basename ./2014_04_09.txt) With this command I can create a archive file 2014_04_09.tb2 ...
82
votes
3answers
7k 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 ...
1
vote
2answers
20 views

Install-on-Demand Wrapper Function for Executables

How do I make the following function work correctly # Install git on demand function git() { if ! type git &> /dev/null; then sudo $APT install git; fi git $*; } by making git $* ...
21
votes
4answers
1k views

Is the shell permitted to optimize out useless terminating commands?

If a shell is asked to perform a probably useless (or partially useless) command known to terminate, such as cat hugeregularfile.txt > /dev/null, can it skip that command's execution (or execute a ...
2
votes
1answer
75 views

How does one determine the amount of space allocated to their command line?

How would one go about determining the amount of space allocated to their system for command lines. Is there anything else I need to be concerned with?
1
vote
1answer
75 views

Linux - How to open a console and display command results on startup?

I have a Linux server with a screen always displaying the end of a very usefull file. How could I automatically enter a shell and display the end of this file when the server starts? I'd like to do ...
4
votes
1answer
318 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 ...
5
votes
3answers
654 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 ...
7
votes
2answers
131 views

what is `env <command>` doing?

What is the command env ls -al doing? I had a Linux test and there was question: "How to run command directly, but not its alias?" I knew that there exists solution like prefixing command with some ...
1
vote
1answer
169 views

What is the extended version of the “sl” command?

Recently I've been discussing Unix humor with a friend and we got to the topic of the sl command. I got the sources, compiled, installed on our development machine, and... got rather disappointed. The ...
3
votes
3answers
435 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 ...
1
vote
2answers
95 views

Using globbing/wildcards when Opening Files from Terminal

I have a folder A. Inside the folder, there are some files a,b,c,d and there is a subfolder, B, containing files e,f,g. Suppose I want to open files a,b,c,d: then I just type xdg-open *. However, ...
3
votes
2answers
304 views

what is the meaning of this sed command?

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}?
3
votes
2answers
433 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 ...
0
votes
1answer
261 views

Unable to execute command in the Linux with an user

Two scenarios here. Sudo rights are given for a particular group. a. A new user is created and is assigned to the group. b. Using this user, when we execute commands via shell script it is unable to ...
1
vote
4answers
191 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 ...
4
votes
1answer
163 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)
0
votes
1answer
579 views

How to run a shell command in a server?

I am fairly familiar with computers and web stuff but this is a bit out of my comfort zone. I have a shell script (.sh file) I want to run in a Linux server I have one site hosted (the script is a ...
0
votes
4answers
3k views

How to create custom commands in Unix/Linux? [closed]

I'm a newbie in Unix/Linux environment. Can anyone guide me to create custom commands in Unix/Linux. Thanks in advance
1
vote
1answer
92 views

Find if a process terminates in a specific amount of time

I am running a program.Inside this program i run a specific command and i use ulimit command to terminate the running of that command if it exceeds an amount of time.To be more clear i run this: ...
0
votes
2answers
1k 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 ...
1
vote
2answers
167 views

Best way to call command within a shell function having the same name [duplicate]

I like to encapsulate commands within shell-functions using the same name. But to avoid the shell-function calling itself recursively, I specify the complete path of the command as the following ...
1
vote
1answer
886 views

What does sourcing a file mean in a shell? [duplicate]

Possible Duplicate: Different ways to execute a shell script What happens when I issue the following command: source devenv.csh How does it differ from running it just as devenv.csh ?
2
votes
4answers
490 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 ...
1
vote
2answers
4k views

tar: Unexpected EOF in archive

I am trying extract .tar.gz file it but with no luck gzip: stdin: unexpected end of file tar: Unexpected EOF in archive tar: Unexpected EOF in archive tar: Error is not recoverable: exiting now the ...
5
votes
3answers
923 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
4
votes
3answers
2k 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): ...
11
votes
2answers
6k views

How to run time on multiple commands AND write the time output to file?

I want to run time command to measure time of several commands. What I want to do is: Measure the time of running of all of them added together Write the time output to a file Write the STDERR from ...
0
votes
2answers
188 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 ...
5
votes
3answers
464 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 ...
3
votes
1answer
1k 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: ...
75
votes
6answers
6k 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?
3
votes
1answer
519 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 ...
18
votes
3answers
770 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: ...
3
votes
2answers
2k 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
2
votes
3answers
2k 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/'
4
votes
5answers
945 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}' ...