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, …).

learn more… | top users | synonyms (1)

2
votes
1answer
13k 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
107 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
584 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
760 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
3k 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
928 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" $ ...
0
votes
1answer
491 views

How to undo DISPLAY export in linux?

I have exported my X display to another computer using this command: export DISPLAY=xxx.xxx.xxx.xxx:0.0 How can I undo it?
0
votes
1answer
566 views

Test variable if its string or not

I'm writing a script which will have some arguments and so I am using getopts but i want to solve the problem with one argument. I use a switch, for example -d, and I want the argument for -d will ...
84
votes
4answers
2k views

Can I somehow add a “&& prog2” to an already running prog1?

Most shells provide functions like && and ; to chain the execution of commands in certain ways. But what if a command is already running, can I still somehow add another command to be executed ...
1
vote
2answers
2k views

Tab auto completion doesn't work with apt-get install (kubuntu)

I've noticed a strange behavior of my shell on Kubuntu. Auto completion doesn't work well when I try to install new software. It works only for default commands (when I type "apt-get inst" and I press ...
1
vote
1answer
583 views

Execute command on remote host fails

I'm trying to execute some commands on remote host like this : ssh -t -t -l user 172.20.20.20 <<EOF pid=$(ps -ef | grep [a]pp-management | awk '{print $2}') && kill -9 $pid && ...
0
votes
2answers
315 views

Using Pipeline to Direct Files to Program that Opens Them

I have a Music folder, in which I have some music tracks, which aren't organized too well. Thus, if I want to find a particular track, I usually type: ls Music | grep <keyword>, where <...
14
votes
2answers
8k views

Difference between executing multiple commands with && and ; [duplicate]

What's the difference between executing multiple commands with && and ;? Examples: echo "Hi\!" && echo "How are you?" and echo "Hi\!"; echo "How are you?"
14
votes
2answers
832 views

What does redirection with >| do?

When should you use >| for redirecting output to a file instead of just >? The explanation given when I was shown this was that it guaranteed the target file was truncated first. But I thought ...
5
votes
2answers
18k 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 ...
4
votes
1answer
346 views

How can there be a directory named `~`?

I was trying to test out this buggy/new tool to see how it works, and it prompted me to choose a directory to use for stuff I am doing. From the directory ~/Code/indep, I typed in ~/Code/indep/tarbell....
3
votes
1answer
12k views

Appending to same array in various loops, only last values remain Bash 4

I have something like this: FILES=() for i in *.map do FILES+=($i) done find /var/candy -name "chocolate_[0-9]" | while read snack do FILES+=($snack) done for file in ../out/amsterdam/...
2
votes
2answers
199 views

What is the “initialization time” in the find command?

When I try to refer find command's man page , I come across -mmin n The value of n can be one of the following: n Evaluates as True if the file modification time ...
4
votes
4answers
1k views

How can I grep for a string containing regex metacharacters like $ and '?

I want to search all files in the current directory and below for the substring $form['#node']. So, I have tried, initially: grep -R "\$form\[\\\\'" . and grep -R "\$form\[\'" . But it returns no ...
1
vote
1answer
833 views

Read a variable with “read” and preserve backslashes entered by the user

I'm using read to read a path from a user like so: read -p "Input the file name: " FilePath The user now enters this string: \Supernova\projects\ui\nebula What can I do to replace \ with /. The ...
7
votes
1answer
5k views

How to merge two files in corresponding row?

Now,I have two files: aaaa.txt: a=0; b=1; c=2; bbbb.txt: d=3 e=4 f=5 I want to merge aaaa.txt and bbbb.txt to cccc.txt. cccc.txt as follow: a=0;d=3 b=1;e=4 c=2;f=5 So, what can I do for ...
2
votes
3answers
135 views

What is the language that appears on the first line of a script? [duplicate]

Bash scripts start with the following line #!/bin/bash # Rest of script below ... In bash the # character is the start of a comment, but #!/bin/bash is definitely not a comment, therefore it isn't ...
2
votes
3answers
3k views

Programmatically extract private IP address(es)

I'm looking for an easy way to programmatically extract the private IPv4 address(es) of a computer. Something similar to this question, but restricted to private IPs. As an example, I can extract ...
52
votes
5answers
5k views

Why does no one use the true Bourne shell as /bin/sh?

I've noticed that basically no system I've ever worked with has /bin/sh as a real executable. It's always a symlink to dash, bash in POSIX mode, or something similar. Why? What are the disadvantages ...
5
votes
1answer
260 views

Whys is there extra dot at the start of some command I'm supposed to execute [duplicate]

I've downloaded an installation package of weblogic server and in the README, there's this command to execute: Linux/Mac $ . ./configure.sh It's not the first time I see this. Why is there an extra ...
6
votes
1answer
1k views

getaddrinfo() from shell? [duplicate]

When you call ping name.domain, it goes through both /etc/hosts and the DNS resolver to obtain an IP. It could be an IP hard-coded in /etc/hosts, or it could be one from the DNS server. It does so by ...
3
votes
1answer
223 views

Making an alias which maps arguments to the middle of the command

I want to alias killapp X to pidof X | xargs kill or kill `pidof X`, but I can't think of a way to do this with just an alias on killapp. How could I do this so I don't have to do killapp X` ?
2
votes
2answers
38 views

Inserting favorites into shell console

Is there any tool/terminal emulator which supports that I can insert my 'favourites' like '2>/dev/null' or 'date +%Y%m%d%H%M' and so forth .. everywhere into the command line ? I could not find any ...
2
votes
0answers
157 views

Segmentation fault with dialog [closed]

I'm getting a segmentation fault with the following script when it's more that one child dir past the pwd. The program kills with the error message and I have to reset the shell. For example: I start ...
1
vote
2answers
879 views

Display the number of bytes, words and lines in a file

I want to create a shell script df. As, I want to type in df name_of_file and then I can get the contents of the file. If the file name is in the directory, I want it to show its contents. If not, I ...
4
votes
3answers
4k views

using awk to split a line on single spaces not multiples

I'm trying to split a line that I have no control over the format of. If parameter 7 and 8 are missing which is possible they will be replaced by a space so I would end up with, field1 field2 field3 ...
4
votes
2answers
2k views

creating variable using variable value as part of new variable name

I'm trying to create a new variable using the value of an existing variable as part of the variable name. filemsg"$word1"=" " I've also tried filemsg$word1=" " filemsg${word1}=" " on all ...
0
votes
2answers
845 views

Checking if one of 4 variables starts with string &red in ksh

I'm trying to check if one of 4 variables starts with the string "&red" and I'm struggling to get the match to work. At the moment I've got this, if [[ $filemsgCICS = "&red"* || $...
8
votes
4answers
20k views

What is the difference between echo `date`, echo “`date`”, and echo '`date`'?

What is the difference between these three commands? echo `date` echo "`date`" echo '`date`' I am confused on what the differences actually are. I think that when the ' are around it means that it ...
0
votes
2answers
46 views

Merge source files with destination, replacing older ones

I'm looking for the linux equivalent of the DOS command: xcopy from/* to/* /s/e/d/y Which copies over all new files and only replaces old ones. I'll be running this from the terminal of a Mac OSX ...
1
vote
2answers
62 views

copy a section of data from stdin [closed]

I am running a script that takes its input from stdin. This input can end up being very large so I want to extract the part I'm interested in to a temp file. The first line contains "[cics]" and I ...
2
votes
1answer
1k views

How to echo in shell script without executing the result

I am using this code to print all open files in the specified changelist. while read line; do echo "$line" done < `p4 opened -c $changelist` However, the line also gets executed and I get ...
2
votes
2answers
409 views

What is the use of “&>>” in bash?

I was studying a bash script code where I encountered operator "&>>". I didn't understand its use. So, I referred to http://www.gnu.org/software/bash/manual/html_node/Redirections.html . It is ...
15
votes
8answers
4k views

How to cd automatically after git clone?

I want to automatically cd to the directory created by the clone command after I git cloned something. Important: I don't want to alter the syntax for the command (e.g. use an alias/function) because ...
3
votes
2answers
57 views

Overriding amended time stamps

I need to make it so the files in current directory get amended with a timestamp. It works fine for the first time, but once I run it again it adds another timestamp to the file. I need a way to ...
1
vote
2answers
1k views

Bash completion throwing syntax error

THE PROBLEM: Say I'm trying to change to a directory called 'build' which is in the directory I'm currently in. I start: cd b Then I hit tab once (knowing that no other directories in the current ...
4
votes
1answer
806 views

Array Cartesian product in bash

Is there a way to generate cartesian product of arrays without using loops in bash? One can use curly brackets to do a similar thing: echo {a,b,c}+{1,2,3} a+1 a+2 a+3 b+1 b+2 b+3 c+1 c+2 c+3 but I ...
26
votes
6answers
4k views

Pipe to multiple files in the shell

I have an application which will produce a large amount of data which I do not wish to store onto the disk. The application mostly outputs data which I do not wish to use, but a set of useful ...
3
votes
2answers
655 views

List all dotfiles current directory using zsh

How can I list all dotfiles in a directory using zsh.?
8
votes
5answers
31k views

How to find and replace string without use command Sed?

As we all know, sed is greatly efficient to find and replace string, for example find 'a' and replace it to 'b': sed 's/a/b/g'. Is it possible to do this with other command or shell script instead ...
0
votes
1answer
2k 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 ...
7
votes
1answer
1k views

IFS null is not the same as unset IFS?

I read a great question on here called Understanding IFS. I was surprised because the answers and comments quote POSIX which states that IFS= is not the same as unsetting IFS. If you unset IFS, ...
5
votes
3answers
690 views

Transactional UNIX shell for file system changes

It is easy to make a mistake when copying (cp), moving/renaming (mv), removing (rm/rmdir), creating dirs (mkdir), and changing file permissions (chmod). It would be nice to have a log to view before ...
4
votes
1answer
310 views

Zsh completion that is insensitive between `_` and `-`

I don't like typing underscores, and would like to type a dash instead, and have zsh autocompletion treat it like it could be either a dash or an underscore. Is this possible with built-in zsh ...
3
votes
3answers
2k views

Running tcpdump, tee and scp

I'm trying to run the following: $ tcpdump -l -X -i eth1 -n tcp port <port> | tee capture.txt | \ scp capture.txt root@10.3.3.227:/home/checker/ tcpdump -l -X -i eth1 -n tcp port <...