The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks. Use this tag for questions applying to /bin/sh and most compatible shells (ash, bash, ksh, zsh, …).

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1k views

Make my own basic shell [closed]

I know there are a hundred ways of doing this, but I'm just asking what is the most common way: How do I make my own terminal prompt? In other words, I want something like the shell where I type a ...
2
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2answers
232 views

Convert numeric string from file to exit code in shell

I'd like to grep /etc/password for a username and return the last two digits of a user-id number as the return code. This is because I have an application whose main way of interacting with other ...
0
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1answer
115 views

How to to login to my emailbox using shell or java code [closed]

I want to write a program/script that can send emails on my behalf using Unix Shell or Java. I think Unix Shell would be the best option as I need to do set specific time to send emails from my ...
13
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2answers
8k 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 ...
5
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3answers
3k views

cp doesn't work in script but works in terminal

Now, this is a strange problem, I have this kind of script: CWD="$(cd -P -- "$(dirname -- "$0")" && pwd -P)" RESOURCES_PATH="${CWD}/resources" PROJECT_NAME="something" ...
2
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2answers
282 views

Replicate a directory and file names n times

I have folder which has some data (files) in that with the name 201311261418 And a file 201311261418.eob In my scenario I need to replicate this folder and file names n times with the appended ...
3
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1answer
335 views

Bash to print out the make result

To compile my project and to check if it's good or not, I want to print out the status message after make command. Which one should I use? make && echo “Success” || echo “Fail” make || echo ...
3
votes
3answers
3k views

Cut a field in a string with bash

I need to lower all upper-cases of file and folder names from a path, recursively inside other folders found; I need to do that with a bash script. Here my code: for file in $(find $1 -type f) do ...
0
votes
2answers
132 views

Concatenate a folder's Java files, with a header for each file

I have an obligation to provide a document which just contains every source code file, with the file's name before each file. Example: ============================= src/com/example/Factory.java ...
7
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3answers
509 views

What's the difference between && and ; when forking sleep to background?

I have just asked a question about forking a process to sleep in the backgroud. The notation I came up with myself looks like this: sleep 10 && echo "hello world" & This answer to a ...
3
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4answers
804 views

How do you find what keys the “erase” and “line-kill” characters are in Ubuntu?

I'm new to Unix and have bought today a copy of "The Unix Programming Environment". I'm trying out the stuff from the book. But some of them are not working as expected like : To kill a line and ...
2
votes
1answer
200 views

What does the expression ${MYVAR:+-x} mean in bash?

In a bash script I cannot post here I see the following expression: ${MYVAR:+-x} I understand the meaning of expressions like ${MYVAR:+OTHERVAR} and ${MYVAR:-OTHERVAR}, but an expression with both ...
2
votes
1answer
430 views

What does the expression $(<“dir/file”) mean in bash?

In a bash script I cannot post here I see the following expression: $(<"dir/file") From what I understand the expression $(...) evaluates a command inside (as when using backticks), but what is ...
3
votes
1answer
393 views

Getting size of directories and exclude some folders

I have an directory structure like this: application1 application1_edit application2 application2_edit Is there any way to get the total size for every folder (including sub-directories) and ...
4
votes
4answers
7k views

What is the most efficient way to move a large number of files that reside in a single directory?

CentOS 5.x I apologize if this is a repeat question. I've seen a lot of similar questions (regarding deleting files) but not exactly the same scenario. I have a directory containing hundreds of ...
10
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6answers
10k views

Run script in current shell without . before command

If a script should be executed in the current shell, it can be achieved by adding a dot before the command: . ./somescript.sh Is there a way to do this without typing the dot every time? For ...
11
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4answers
307 views

How to “combine” lines printed by multiple programs safely?

Suppose I want to execute multiple programs in parallel and combine their outputs to one pipe: sh -c ' (echo qqq; echo qqq2; echo qqq3)& (echo www; echo www2; echo www3)& (echo ...
8
votes
3answers
2k views

Redirect output from all commands to file, not just last

I want to add a header to a file with echo, then use a command to create the rest of the file. This means I'll be using two separate commands. How do I write the output from both commands to a file ...
14
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2answers
40k views

Remove all files created before a certain date

I have a directory containing a high number of files (like logs for every day of the year). I would like to remove all files created before let's say 22/11. How can I achieve that ? Must I use find ...
4
votes
1answer
182 views

`cd` up the canonical path

Consider: $ pwd /home/user $ ls -l total 3604 lrwxrwxrwx 1 user user 19 Nov 27 12:11 pages -> /var/www/pages/ $ cd pages $ pwd /home/user/pages $ readlink -f . /var/www/pages $ cd .. $ readlink ...
2
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1answer
1k 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 ...
6
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3answers
174 views

How can I determine a file's conventional filename extension

The file command is good at determining file types for my needs. Is there any way to map those results to conventional filename extensions?
3
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2answers
509 views

Is there a hook-like system for shell?

I noticed I like to execute certain actions in a specific order. A hook, as I see it, is basically "do something after event", where event, could be any command with parameters, such as git clone, ...
4
votes
2answers
928 views

Gaussian, which is run with nohup on remote linux machine, gets killed when the local computer is powered down before the shell is exited

I have a problem running Gaussian on remote Linux via SecureCRT on Windows. Gaussian Gaussian spawns different child executables ("link"s) when running. For example, I start Gaussian by running ...
2
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2answers
250 views

turn off buffering for `hping` in OpenBSD

It would appear that the output from hping is fully buffered when piped to perl for further line-by-line processing, so piping hping to perl doesn't work. hping --icmp-ts example.ca | perl -ne 'if ...
0
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1answer
87 views

What's meaning the of a pair of parentheses after a string literal?

I accidentally input the the following command into the Bash terminal: exit() And the Bash keeps read the next line until I input a string literal and Bash gives the error of "-bash: syntax error ...
6
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2answers
325 views

Why two almost idetical grep commands return different output: w/o and with filename

I have 2 almost identical greps: [Alex@localhost tmp]$ grep /bin/bash /etc/passwd root:x:0:0:root:/root:/bin/bash AlexL:x:500:500::/home/AlexL:/bin/bash user1:x:501:501:user1 ...
2
votes
1answer
174 views

date doesn't accept its own output

What is the option for date to give output in a format acceptable to date --set ? I'm trying to remotely set the date, using the current computer clock of my workstation. ssh user@host sudo date ...
1
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2answers
136 views

"trap 'killall $$ ; rm -f $folder2;exit ' 18 20 24

What is wrong with this command? $ trap 'killall $$ ; rm -f $folder2;exit ' 18 20 24 That command is in a for loop, and while that for is executing, if I press CTRL-Z I want it to stop the process ...
0
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2answers
235 views

Run an SSH command on two hosts whose name comes from another command

So what I'm trying to do should be fairly simple but I can't seem to figure it out. I need to kill a certain process on different boxes, they all have a defined IP range although they will eventually ...
1
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1answer
3k views

A command that gives username@hostname:pwd

I know that pwd gives the current working directory, hostname gives the current host and whoami gives the current user. Is there a single unix command that will give me the output of ...
10
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2answers
1k views

Cannot expand asterisk without proper permission

Can someone explain to me the following? $ ls -ld /temp/sit/build/ dr-xr-s--- 3 asdf qwer 4096 Jan 31 2012 /temp/sit/build/ $ ls -ld /temp/sit/build/* ls: /temp/sit/build/*: Permission denied So ...
2
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1answer
514 views

Why is the restart inittab action asking me for an id?

I am following the NAND firmware update tutorial to try to get my system to run from RAM so I can flash it. I previously had my script running but for some reason unknown to me it is giving me: INIT: ...
3
votes
3answers
972 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
4answers
264 views

saving output of another command

I need to select certain lines from the log file and also save them to a text file. I tried the following but none of them are working as expected. The file "todel.txt" shows 0 bytes. tail -f ...
1
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1answer
178 views

How can I create a variable for just the Size, Used, and Available of df?

Say I want to create variables, one for each the size, used, and available when using df. How can I create variables for each? Is there an option that returns just one of these things? directorySize= ...
0
votes
1answer
6k views

MySql not accessible by root user

I have a local MySql server. It is started as I can access it with my local user like $ mysql Welcome to the MySQL monitor. Commands end with ; or \g. Your MySQL connection id is 66 Server version: ...
10
votes
5answers
16k views

How to remove blank lines from a file in shell?

I want to remove all empty lines from a file. Even if the line contains spaces or tabs it should also be removed.
3
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1answer
2k views

Granting access to a restricted git shell

I tried setting up git-shell on our CentOS (6.4) system (after getting this working correctly on Ubuntu 13.10, maybe cross platform hot mess?) my /etc/passwd shows git:x:500:500:Web Archive ...
1
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2answers
255 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, ...
1
vote
2answers
344 views

What does this regex mean?

I was working on the conversion of Unix newline to Windows newline. I tried to unix2dos but it gave me some binary error, so I looked it up and stumbled upon this regex sed 's/$'"/`echo \\\r`/" ...
1
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3answers
3k views

Remove all *.mp4 and *.zip but some files

In one of my programs I call a bash command to remove all files in the directory, but some: bash -c shopt -s extglob shopt -s nullglob rm /path/to/directory/!("file1" | "file2") Which for what I ...
16
votes
2answers
818 views

How can I stream data to a program that expects to read data from a file that is given as a argument?

I have a huge gzipped file and I want a program (4s-import in this case) to read it. It takes a lot of time to first unzip the file and then call the program with the path to the file as an argument. ...
6
votes
5answers
44k views

How to start a program in the background

The program Boblight does not run in background. There is no noticeable difference between executing sudo boblightd and sudo boblightd& How can I solve this problem that the console will ...
2
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1answer
10k views

How to change permissions from root user to all users?

I created a folder on the command line as the root user. Now I want to edit it and its contents in GUI mode. How do I change the permissions on it to allow me to do this?
2
votes
2answers
106 views

Capturing the name of the file pointed by a symbolic link in a variable

Say I have a symbolic link: /path/to/foo->/path/to/some_file.txt Say I have a shell variable x=/path/to/foo, how can I get some_file.txt in a shell variable y?
3
votes
1answer
547 views

present users a login prompt? /bin/login? getty?

I have a service that execs a command when a user connects to it through a socket, and redirects everything it receives to the executed program. It works ok with shells like bash, giving the user a ...
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}?
4
votes
3answers
2k views

Weird “No such file” error with “xargs” and “file”

I'd like to get the MIME type of all files under the current directory. Why doesn't this work? I've tested bash on OSX or Linux. "file" complains that it can't find the file, but if I run it with the ...
4
votes
2answers
873 views

Word-splitting when parameter is used within command substitution

What needs to be done to ensure that a parameter containing embedded spaces is handled correctly when used within a command substitution? Perhaps an example will illustrate $ file="/home/1_cr/xy z" $ ...