The shell is unix's command-line interface. You can type commands in a shell interactively, or write scripts to automate tasks.
1
vote
2answers
25 views
how does built in commands of a shell implemented in Linux? as a function or thread of shell process?
I know that external commands are run in the shell by creating a separate process. But what exactly happens when a built in command is run in a shell.
Are they executed as a function or if the shell ...
0
votes
3answers
38 views
Is there a way to switch to “su -” after switching users through “su”?
Maybe the title wasn't worded quite clear. But basically what I want to be able to do is to switch to having used "su -" instead of the traditional hyphenless "su" after already using "su" to switch ...
2
votes
3answers
41 views
Why do 'ssh host echo $PATH' and printing the $PATH after ssh'ing into the machine give different results?
On a particular host, when I ssh into the machine and enter echo $PATH I get
/home/wxy/bin64:/home/wxy/bin:/usr/kerberos/bin:/usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/bin:/usr/bin
and if I ...
-3
votes
1answer
50 views
“not a valid identifier” when I do “export $PATH”
When I run export $PATH in bash, I get the error not a valid identifier. Why?
Here's my ~/.bashrc file
# ~/.bashrc: executed by bash(1) for non-login shells.
# see ...
3
votes
1answer
71 views
How to trigger error using Trap command
I am using Ubuntu 12.04.2. I am trying to use "trap" command to capture abnormal or error in my shell script but I am also trying to manually trigger "Error" exit.
I have tried exit 1, but it won't ...
0
votes
0answers
31 views
Easy way to push data into MongoDB from Bash shell script?
I know you can create a Javascript file that the MongoDB shell will execute upon startup. But I'm hoping for something more "lightweight" than that. I am using a Linux program that has a scripting ...
3
votes
2answers
54 views
cd to directory of a symbolically linked file
Before I write a script, anyone know an easy way to do the following:
$ pwd
/foo/bar
$ ls -l
lrwxr-xr-x 1 username admin 48 Apr 17 2012 foo.sh -> /bar/foo.sh
$ cd /bar
$ ls
foo.sh
i.e., in ...
6
votes
2answers
185 views
Executing piped commands in parallel
Consider the following scenario. I have two programs A and B. Program A outputs to stdout lines of strings while program B process lines from stdin. The way to use these two programs is of course
...
4
votes
3answers
61 views
Terminating a bash shell script running in the background
I often use bash shell scripts to run simple commands for many different files. For example, suppose that I have the following bash shell script, called script.sh, that runs the program/command foo ...
-1
votes
1answer
46 views
SED command and filenames with space
I was hacked, for my php files was infected.
Example: http://www.nwww.ma.mk/oscommerce/configweb/apexfash-wp-blog.txt
Bad Code:
<?php ...
0
votes
2answers
29 views
Why are there empty lines in the output of my command?: find ~/x/y/ | shuf > ~/Desktop/z.txt
As it turns out the reason for this problem was one filename with several newlines. (No idea how that happened.)
find ~/x/y/ | shuf > ~/Desktop/z.txt
This command works pretty much as expected ...
4
votes
2answers
42 views
Convert MAC address to Link-local address with bash
How can I convert a Mac address into an ipv6 Link-Local address?
you have to add fe80:: at the start and insert ff:fe in the middle
furthermore all leading zeros must be stripped
3
votes
2answers
51 views
how to loop through arguments in a bash script
I would like to write a bash script with unknown amount of arguments.
How can I walk through these arguments and do something with them?
A wrong attempt would look like this:
#!/bin/bash
for i in ...
4
votes
4answers
61 views
How to deal with spaces in a variable
I'm working on some scripting:
for x in `find ./ -name *.pdf`
do
echo pathname $x
done
My filenames are Test1 ( Volume II), Test2 ( Volume II).
I'm getting a return of
pathname Test1
pathname (
...
-1
votes
1answer
44 views
Strange combination of symbols UNIX [closed]
I was looking at one korn shell script examples and I saw this strange combination of symbols: %?
So my question is what does it mean?
3
votes
2answers
41 views
Do redirection operators always open file descriptors in parallel?
1. Consider snippet#1:
$ cat test.txt > test.txt
cat: test.txt: input file is output file
It seems that cat makes its input file descriptor point to test.txt and then when it tries to set its ...
2
votes
1answer
35 views
Is there a text-only equivalent (no curses) of `zenity --question`?
For my mercurial commit hook, I want to run my test cases and be asked whether I really want to commit if any of the tests fail. I'm thinking something like <run-the-tests> || ...
3
votes
2answers
68 views
Quoted vs unquoted string expansion
for i in $(xrandr); do echo "$i" ; done
for i in "$(xrandr)"; do echo "$i"; done
for i in "$(xrandr)"; do echo $i; done
I understand why 1 differs from 2. But why does 3 give a different output ...
1
vote
2answers
47 views
Shell hangs when doing command from ssh
I'm trying to automate a server update process.
What this should do is check for git diff files and list them, to later be copied from one place to the other.
Here's my script on my local machine:
...
5
votes
7answers
106 views
Bash way to check if a process is already running in the background (and skip re-execution based on that)?
Can I make a bash command line that only runs a certain command if the process is not already running (in the background)?
How do I check*, if a command is already running?
(so I can add the next ...
2
votes
4answers
52 views
1
vote
2answers
58 views
Debugging bash functions [closed]
So here I have a simple function that I wish to debug. However, I am unable to debug the desired function even with set -o functrace enabled. Before resorting to asking this question, I had managed ...
1
vote
1answer
31 views
How can I convert this bash function to the fish shell
I'm trying out the fish shell 2.0 to replace bash. I'm trying to convert the following bash function to a fish function, but its giving me hell. I have a several similar functions so if someone ...
3
votes
1answer
47 views
Cron job results are different from executing from own shell
I am using Ubuntu 12.0.4
I have a script basically with the following codes:
lockfile=/var/tmp/mylock
if ( set -o noclobber; echo "$$" > "$lockfile") 2> /dev/null; then
exit_normally ...
4
votes
3answers
90 views
How to alias cp with cp -i by default
Is there a good way to alias the command cp file1 file2 to cp -i file1 file2?
Apologies if this is a dumb question, I'm a Unix novice.
2
votes
5answers
62 views
Carriage return issue
I have this in a bash script
DAY2="20130605"<Cr>
echo "This is yesterday date:"$DAY2"end"
Why is the output the following? It seems as though there is a carriage return in DAY2 but where is ...
3
votes
3answers
41 views
How to make my tmux which starts via crontab @reboot use bash?
I have a crontab which launches tmux-launching-script as follows :
-sh-3.00# crontab -l
@reboot /root/scripts/tmux_autostart.sh
where
#!/bin/bash
# setup tmux session
tmux new -d -s my_session
...
2
votes
2answers
117 views
Which is more idiomatic in a bash script: `|| true` or `|| :`?
I don't do terribly much shell scripting, so I was a little surprised when I was reading the documentation for git submodule and I saw the syntax they used in this documentation:
A non-zero return ...
1
vote
1answer
23 views
7z getting an event not found error in command line
I am using 7zip on my centos machine and ziping a file via command line.
This is my syntax
7za a -t7z backup.7z public_html\ -mx0 -xr!restricted_area
What i'm expecting with this syntax is to ...
2
votes
5answers
204 views
In linux, how to delete all files EXCEPT the pattern *.txt?
I know how to delete all txt file under current directory by rm *.txt.
Does anyone know how to delete all files in current directory EXCEPT txt file?
2
votes
4answers
63 views
sh and grep numbers only
I'm facing a problem and trying to find a solution that works in sh.
If I could use bash this code would work:
ls /a|grep ^[0-9]
Unfortunately this is not the case with sh, and yes I need to use ...
2
votes
3answers
68 views
How to use arguments with 'find -exec'? [duplicate]
I'm trying to generate static html files for all php scripts inside dir:
find . -name "*.php" -exec php {} > {}.html \;
But it just dumps all results to {}.html. How to do it properly? And how ...
0
votes
0answers
29 views
How do I make www-data run vim command (and find plugins)
I use the vimwiki plugin for note taking, and for those rare cases when I can't reach my home server over ssh, I use a simple html-form to update the textfiles. In vimwiki there is a command to export ...
2
votes
1answer
54 views
How can I background a shell script during a Kickstart?
I have a Red Hat Kickstart process which reports its progress at key points via a POST request to a status server.
This is fine during %pre and %post, but when the actual build is taking place ...
-1
votes
3answers
81 views
Get environment variable of other user [closed]
Is there a way I can see the environment variable of an other user? I want to do that as root, so permissions won't be a problem I guess.
For the user himself, I use echo $PATH or set | grep PATH ...
0
votes
1answer
44 views
How to identify error in a particular file while checksum verification (which file having problem while verification) in shell script
I have two files on ftp location in csv.gz format and their checksum is in .csv.gz.md5 format. I am copying this file in my local system. I am generating check sum for it through md5sum. Now I am ...
0
votes
1answer
40 views
when to use double quotes with a variable in shell script? [duplicate]
I am in a confusion with what is meant by the double quotes referring to a variable. For example following two scripts gives the same output. What is really meant by the double quotes?
Script1
...
0
votes
0answers
24 views
Parameters of script [duplicate]
how can I make my script to work like that: "scriptname.ksh -p file, -n UserName". I mean how can I set my script to work with 2 parameters defined by "-p" and "-n" characters?
1
vote
0answers
27 views
service command: Failed to issue method call
I downloaded the source of tinyproxy and then use ./configure make make install to install it
Then I want to start it, but get errors, like the following:
[root@kitty tinyproxy-1.8.3]# service ...
4
votes
2answers
113 views
Is it possible to restrict certain commands from being run in a directory?
I have two directories: src and projects. I would like to prevent myself from running git ... unless I am specifically inside src or projects. Is this possible?
1
vote
2answers
63 views
Running a bash script within a bash script
I am writing a bash script for the installation of an environment manager but it means that I have to install something within multiple directories. See my other question for more details. But this ...
0
votes
1answer
55 views
Bash script installing within multiple directories [closed]
I am attempting to write a bash script that will install rbenv from beginning to end. I am on a Mac for interest sake.
But there are some things that are not working mainly i am changing the ...
1
vote
0answers
40 views
add audio from playing file to microphone stream
I need to add a sound to what the microphone is capturing, is it possible?
I started with
man aplay
and found that I can do
aplay -D PCMdevice filepath.wav
so then I listed the PCM devices with
...
1
vote
1answer
38 views
Cut + Copy + Paste in Linux Puppy Wary
Trying to cut + copy + paste from the standard urxvt shell in Puppy Linux Wary 5.3.
If I follow this post on http://crunchbang.org/forums/viewtopic.php?id=15085
and I press:
in urxvt: ctrl + ...
6
votes
3answers
235 views
Why not use pathless shebangs?
Is it possible to have a shebang that, instead of specifying a path to an interpreter, it has the name of the interpreter, and lets the shell find it through $PATH?
If not, is there a reason why?
1
vote
1answer
39 views
How to stop CACHE instance from Shell Script
I want to restart CACHE(database that I am using) Instance from shell script. What I did is created a function in the shell script named resatrt_cache.
restart_cache()
{
ccontrol stop instancename ...
2
votes
1answer
39 views
broken pipe error with popen and JS ffi
I am using a ffi for nodejs which for the most part has nothing to do with this question which is really about understanding pipes better, but does offer some context
function exec(cmd) {
var ...
3
votes
1answer
42 views
find utility does not recognize bracket notation
I've two files in the current folder:
submitWeb.m
submit.m
the following find does not show the two files:
find . -regex .*submit\(Web\)?\.m
But the above regex expression works fine in ...
2
votes
2answers
133 views
mv: cannot stat No such file or directory in shell script
I wrote a script to move some files form one folder to another folder
but I got the following error, I checked 2 folders and notice for 1 folder there are such files and another there is no such ...
1
vote
2answers
62 views
cat files in current folder and all subfolders [duplicate]
I want to cat a file in current folder and all files in all subfolders (and subsubfolders).
Here is my directory structure
$ tree
.
├── f
│ └── foo
└── yo
I want to cat foo and yo.
I've tried ...
