Tagged Questions

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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3
votes
1answer
19 views

Why does unbuffer command affect time command?

I noticed something odd when using the unbuffer command with time command. Here I just want to see how long takes to find a certain file in my system: time find . -name unixstuff output is : ...
8
votes
2answers
193 views

Precedence of && vs & in bash and zsh

Answering this question I discovered a very funny (and subtle) difference between behavior in bash and zsh: In bash: romano@RRyS:~$ pwd /home/romano romano@RRyS:~$ alias x="cd /bin && ...
1
vote
1answer
34 views

No prompt after logging in

After entering my username and password when trying to log in, I am not getting the command prompt. This is what my screen looks like: pal login: root Password: Last login: Wed Oct 14 15:42:19 on ...
2
votes
4answers
163 views

How to read certain lines after a find some text?

How i can read a certain number of lines after find some text? Eg.: Read next 2 lines after find "Unix" on: Test 1 Test 2 Test 3 Test 4 UNIX Test 5 Test 6 Test 7 Test 8 Test 9 Result can be: ...
7
votes
3answers
231 views

Empty a file without grep subsequently treating it like a binary file

Currently I have netcat piping output to tee which is writing to output.txt with nc -l -k -p 9100 | tee output.txt I want to monitor this output, so I'm watching it with tail -f | egrep -i 'regex' ...
1
vote
2answers
67 views

Check that a bash script has exactly two arguments which are directories

I'm writing a bash script that compares two directories, but I'm not sure how to check conditions For example, if the user enters 1 arg instead of 2 (we need 2 since we're comparing two directories), ...
2
votes
2answers
31 views

Clear or disable aliases in zsh

I installed oh-my-zsh to make terminal use a bit easier. One thing that bugs me though is the prolific aliases added by it, like "ga", "gap", "gcmsg", "_", which are harder to remember than the ...
4
votes
4answers
289 views

extract every nth character from a string

I am trying to figure out a solution for this question. My approach to this problem so far is as below. Append all the characters together to make it a long string. After the above step, remove ...
1
vote
1answer
21 views

How to copy with wildcard in directory name?

I would like to copy the html directory inside a directory like cms_drupal_PROJ-1-2 to /var/www. The last digit in the working directory is dynamic so at any given time all I know is ...
0
votes
1answer
23 views

UNIX stdout redirection

I've written a script and I want to direct the console output to a file, so I use this command: ~/simplesim-3.0/sim-cache -cache:dl1 dl1:1:64:2048:f -cache:il1 il1:1:64:2048:f \ -cache:il2 dl2 ...
2
votes
4answers
185 views

Remove file with ` in name

At some point I created a file with: ` in it. How do I remove it? ls -la returns: -rw-rw-r-- 1 ec2-user ec2-user 0 Sep 25 23:01 `which
0
votes
3answers
100 views

Can dash replace bash as my default shell?

From what I read, dash can be made as a shell by using the command ~$ chsh shirish Password: Changing the login shell for shirish Enter the new value, or press ENTER for the default Login Shell ...
5
votes
2answers
692 views

Why doesn't 'sudo bash && cd desktop' cd in to the desktop folder? [duplicate]

I have a folder with chmod 000 permissions on it with a lot of different stuff in, the way I get in is a start bash in sudo by running sudo bash. Why can't I do &&? I want to cd into the ...
0
votes
0answers
20 views

history - bash, dash, zsh and .profile [duplicate]

For a long time I have been wondering about the existence of many shells in GNU/Linux. To make the question a bit focused I have used only three shells - bash, dash and zsh. From wikipedia articles ...
0
votes
1answer
28 views

What is the difference between the built in echo command and /bin/echo? [duplicate]

I was playing around with the type and which commands and I discovered something strange. type either returns the path or says that a command is a Bash built in. which either returns the path or ...
0
votes
0answers
39 views

How to decrease the RAM and Cores for sometime

I have 9 VMs running Ubuntu 12.04.I am using resources from GENI ( Global engineering Network Infrastructure ) to set up topology and i reserved resources with the following configuration. RAM - 4GB ...
3
votes
1answer
31 views

Terminating SSH called from a script (SIGPIPE handling?)

so I was wondering why there are some hanging SSH connection left from some of my automated scripts and I came to a weird issue - SSH, if used without PTY, doesn't terminate when the output pipe gets ...
1
vote
2answers
66 views

How to do a grep on remote machine and print out the line which contains those words?

I have few logs files in my machineB under this directory /opt/ptd/Logs/ as shown below - My logs files are pretty big. david@machineB:/opt/ptd/Logs$ ls -lt -rw-r--r-- 1 david david 49651720 Oct 11 ...
5
votes
1answer
39 views

Representing/quoting NUL on the command line

Can \0 be used on the command line? Background For testing corner cases in GNU Parallel I was curious whether all characters were correctly quoted on the command line. Most of them are: perl -e ...
6
votes
5answers
258 views

Number of characters in a shell command's output

I am writing a script which needs to calculate the number of characters in a command's output in a single step. For example, using the command readlink -f /etc/fstab should return 10 because the ...
4
votes
1answer
83 views

How can I create an alias that passes additional arguments?

I have an executable that I use often: /dir1/dir2/dir3/dir4/executable argv[1] argv[2] argv[3] I know that I can set an alias for the executable: alias myexecutable = ...
0
votes
3answers
28 views

Redirect stderr and stdout to another file descriptor

exec 6>&1 will copy file descriptor 1 onto 6. But how can I copy both stderr and stdout (1 and 2)to file descriptor 6 ?
1
vote
1answer
24 views

Define custom login shell in schroot

According to the schroot man page: schroot allows the user to run a command or a login shell in a chroot environment. If no command is specified, a login shell will be started in the user's ...
3
votes
3answers
131 views

Can you source a “here document”?

Let's say I have a bash script that acts as a config file for another bash script: config.sh: verbose=yes echo "Malicious code!" name=test script.sh: source config.sh echo "After sourcing: ...
2
votes
0answers
39 views

bash syntax error near unexpected token `(' - but everything looks like it should work [duplicate]

I'm trying to write a bash script which will copy a bunch of files and directories from a directory, omitting a couple but taking everything else. I have got a command that does this and works from ...
1
vote
1answer
70 views

One-Click Script to Gmail Yourself a File

Does such a thing exist? I'd be interested in something like: You right-click a file in a file viewing manager, and click "gmail yourself this file". One click, and you're done. You open up the ...
0
votes
1answer
36 views

Shell script permission denied despite +x flag

This is an odd one, it only happens on one server (shared hosting, so I have limited access to configuration and logs), but I can't wrap my head around it. I have a shell script which runs some app's ...
4
votes
2answers
327 views

How to check whether a process is daemon or not?

I have written a small daemon that starts at the boot time and does all the things perfectly like writing in the log file. But I want to know, how can we check whether that process is daemon or not? ...
1
vote
2answers
87 views

bash question about if and then [duplicate]

I'm writing this in my script. It has other parts but I'm getting stuck on this part only. if [[$# == $year $month $day ]] ; then cal $day $month $year fi When I run this it give me this msg: ...
-1
votes
1answer
63 views

just wanted to know what am i doing wrong in the end of this script that doesnt put my checkdate in to cal command

#Purpose: Validate a date #Usage: chkdate year month day # if [ $# -eq 0 ]; then echo Usage: chkdate year month day exit 0 fi year=$1; month=$2; day=$3; extra=$4 if [[ "$extra" != "" ...
0
votes
1answer
41 views

nmap won't recognize a hostname on my local area network

Scanning the machine on the LAN with my laptop, I got this: gabriele @ osiris { ~ } [ Tue Oct 07 ] [ 08:49 PM] nmap -sP 192.168.1.236 Starting Nmap 6.40 ( http://nmap.org ) at 2014-10-07 20:50 CEST ...
2
votes
4answers
199 views

Creating symbolic link recursively

I essentially want to run this command... ln -s /opt/gitlab/embedded/service/gitlab-shell/hooks/ /var/opt/gitlab/git-data/repositories/web/*/hooks This would create a symbolic link in all folders ...
2
votes
3answers
65 views

How to nest quotes in bash commands

I want to test the result of this command: dmesg | grep "Firmware patch 1563" Therefore, I try to write something like this: if [ "`dmesg | grep "Firmware patch 1563`" == "" ] But it doesn't ...
0
votes
1answer
37 views

Options to a command specified in a file

How can I have some of the options to a unix command come from a file? That is the file does not contain all the options -- other options are specified elsewhere. For example I have the ...
2
votes
1answer
66 views

bc behaves differently on Solaris and Linux

I have the following problem that I have not resolved for a long time now. We have a Linux (x86_64 GNU/Linux) server and a Solaris (SunOS 5.10 i86pc Solaris) server where I work. On the linux server, ...
4
votes
2answers
175 views

How to escape single quotes correctly creating an alias

I've been given this one-liner to know how much memory my processes consume. $ ps -u $USER -o pid,rss,command | \ awk '{print $0}{sum+=$2} END {print "Total", sum/1024, "MB"}' Now I'd like to ...
4
votes
2answers
320 views

What are the shell's control and redirection operators?

I often see tutorials online that connect various commands with different symbols. For example: command1 | command2 command1 & command2 command1 || command2 command1 && command2 ...
9
votes
5answers
1k views

Is there a difference between `;` and `&&` and `|`? [duplicate]

When you want to run multiple commands you can use ;, && and | Like this: killall Finder; killall SystemUIServer, cd ~/Desktop/ && rm Caches Or: man grep | man cat for example. But, ...
4
votes
2answers
52 views

How to exchange words in a filename using the shell?

One of my customers is a school. On their file server all projects have a directory with the same naming scheme. <last name>, <first name> <second name>? - <project ...
2
votes
2answers
48 views

Is there an improved version of “pick” that will work with filenames with spaces?

Is there a version of the pick script that will work properly with spaces in the filenames? This is a tricky question—pick is trivial to enhance to work with spaces in filenames, but the output ...
0
votes
1answer
52 views

move files of a particular pattern to another directory

In the directory /home/in I have files like this: crust.MC12345.txt crust.etcMC12345.txt crust.MC23456.txt crust.etcMC23456.txt crust.etctcMC23456.txt I only need to move crust.etcMC12345.txt ...
0
votes
0answers
46 views

Making A Shell Script To Write To XML File

I am writing a shell script to make writing my RSS a whole lot easier. Right now I am stuck at how to properly edit my files. See, I want the program to take in data from me, and then save those to ...
1
vote
1answer
29 views

Using bash environment from an external OS partition

I have an external partition, /dev/sda, which contains an Ubuntu OS. The root is located in /dev/sda2. I would like to access commands from this OS partition. I have tried doing the following ...
2
votes
3answers
67 views

Redirect stderr to a file, but create only if any stderr happened? [duplicate]

I'm running a command like: parallel --spreadstdin --line-buffered 'some_command 2> `mktemp --tmpdir /tmp/stderr`' | do_something The trick is that parallel creates a lot of processes and they ...
1
vote
2answers
28 views

Listing folder contents during cd command

I might be mistaken here, but I was watching someone navigate using the cd command, and without actually executing it, they were able to show the folder contents of the current folder. So if I type ...
17
votes
5answers
2k views

Why do I sometimes get repeatedly prompted with “>” in the terminal?

Alright, when I run certain commands the wrong way, (misspelled, etc.) The terminal outputs this: > instead of computername:workingfolder username$, and when I type enter it goes like this: > ...
0
votes
2answers
50 views

copy and rename script

Directory A: 1111111_1.pdf 2222222_1.pdf 1234567_1.pdf Directory B: abcdefg.pdf zzzzzzz.pdf 1234567.pdf 1111111.pdf 2222222.pdf ...
33
votes
2answers
2k views

How do I open an incognito bash session?

Is it possible to open an incognito session in bash? For example, when we need to enter passwords in commands and don't want bash to add them to history.
0
votes
1answer
52 views

How to wait until script ends - csh?

I execute a script that splits a big file into little files. Immediately afterwards I ask if (-f *filename) then .... Sometimes the script doesn't finish so the if doesn't work. I tried sleep but ...
9
votes
4answers
248 views

Unexpected EOF and syntax error

I am currently writing my third ever shell script and I have run into a problem. This is my script so far: #!/bin/bash echo "choose one of the following options : \ 1) display all current users \ ...