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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Terminal sandbox commands

I was wondering if there's a way to run shell commands that affect only a certain directory and its subdirectories. I'm using PHP and I want to make an app that allows the user to execute shell ...
3
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2answers
329 views

How to get UUID of filesystem given a path?

I am handed a path of a directory or a file. Which utility/shell script will reliably give me the UUID of the file system on which is this directory/file located? By UUID of file system I mean the ...
2
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2answers
115 views

How to return 0 if a pattern is matched from a file? [duplicate]

I have a binary that repacks android kernel (not mkbootimg). I'm making a script to automate the process. I don't want any output on the screen. So I have redirected the output to a file named ...
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2answers
249 views

multiple conversion bam to bed using bedtools

I have ten .bam files (bioinformatic format) and I would like to convert it to 10 .bed files, but for this conversion I need to use special command bedtools bamTobed -i (input file) > output ...
1
vote
1answer
61 views

runtime errors, where do they come from?

When a program is executed from the command line (terminal) and there is a runtime error causing the program to seg-fault/coredump where is the runtime error message come from? Is there documentation ...
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2answers
49 views

“dpkg -l” receives shell wildcard character?

In a bash shell where I have globbing enabled if I execute ls -l *ou*, then shell should pass out.dot and out.png as arguments to ls, i.e. ls never sees the * character. However, looks like in case of ...
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7answers
780 views

Remove a specific extension from all the files in a directory

I have a couple of files with ".old" extension. How can I remove the ".old" extension without remove the file? I can do it manually but with more work: mv file1.key.old file1.key mv ...
2
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3answers
110 views

Is it possible to add a function within a function?

function update_profile { echo "1. Update Name" echo "2. Update Age" echo "3. Update Gender" echo "Enter option: " read option case $option in 1) update_name ;; ...
23
votes
2answers
5k views

What is the bash shortcut to change to the previous directory?

Sadly, I only learned about this last year by stumbling upon it randomly on the internet. I use it so infrequently that I always forget what it is by the time I need it again. How do you change to ...
2
votes
2answers
266 views

Can I create, set permissions, and write to a file with a single Unix command?

I want to speed up creation of user accounts on some Linux VMs that I am creating, and wondered if I could simplify the process of writing to the new user's ~/.ssh/authorized_keys or ...
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2answers
2k views

What is the difference between shell, eshell, and term in Emacs?

In Emacs I can run a shell using following commands - M-x term M-x shell M-x eshell What is the difference between these three?
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5answers
4k views

What are the fundamental differences between the mainstream *NIX shells? [closed]

What are the fundamental differences between the mainstream *NIX shells and what scenarios might prompt you to use one over the other? I understand that some of it probably comes down to user ...
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2answers
118 views

How do I get command name of the last executed command?

Example: I type man ls, than I want to get man only. By using !! I can get man ls but how do I get man?
1
vote
1answer
74 views

difference between “ip link set” and “disconnect / reconnect” in the GUI?

I've got an Ubuntu 14.04 guest installed in virtualbox. Often when the host machine changes networks or is suspended and restarted, the guest VM loses network connectivity. I can reliably get it ...
8
votes
2answers
547 views

Is it possible to use shell parameter variables ($1, …, $@) directly in CLI?

Sometimes it is necessary to emulate and verify the above variables in small examples and then can be copied immediately to some script, etc. I tried to solve by using a simple example in the ...
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votes
3answers
50 views

Diff between (x=100) and { x=100; }?

Can some one please explain the below statements? $ x=50 $ (x=100) #here the code executes only with in the subshell. when subshellexecution done then the x value is returned to its original ...
2
votes
1answer
325 views

How to get binary representations of strings in Shell?

I'm using openssl dgst -sha1 -binary to get hash values of my strings in binary format. (I'm using -binary flag because my version of openssl adds "stdout" before each hash value on default output, ...
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2answers
69 views

How do I tell GCC and Clang to look at /usr/local/cuda for include/libs?

I have installed CUDA on my system, but seems like its files are not being found by libraries that depend on it. What should I append to my .bashrc in order for both GCC and Clang to look on the ...
1
vote
1answer
222 views

Using cURL, How can I fetch a numerical string which contains commas and spaces and convert such to a NON COMAFIED string [duplicate]

Example: Google's Outstanding Shares are 670,000,000 and this value is collected in a txt file from Yahoo Finance API using the below script. The issue is; that numbers WITH commas or spaces are ...
0
votes
2answers
36 views

how to know which device was open

is there any shell command, can let me know, current open device or device already in operation. For example, I use minicom to open a device /dev/ttyUSB0 or /dev/ttyS0, after I use program open this ...
3
votes
1answer
240 views

Mac OS X combine cp and cat to sequentially copy and rename files in list

I am using a MacBook Pro OS X 2013 model. I have a list of filenames in a text file named list.txt separated by line breaks list.txt exactly like this, but this list is going to be long e.jpeg ...
1
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3answers
92 views

How to negate a case pattern

How add I add the condition in case whereby if it does not detect the required conditions, it will execute the command. My code: case $price in [0-9] | "." | "$") echo "Numbers, . , $ Only" ...
0
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1answer
95 views

timeout pipeline

I want to execute these two timeout command on the same command but with a different time and instructions. So timeout --signal=SIGINT 5s command timeout --signal=SIGKILL 10s command How to append ...
192
votes
5answers
12k views

What's the difference between $(stuff) and `stuff`?

There are two syntaxes for command substitution: with dollar-parentheses and with backticks. Running top -p $(pidof init) and top -p `pidof init` gives the same output. Are these two ways of doing the ...
42
votes
5answers
21k views

How to go to the previous working directory in terminal?

In terminal, how can I define a key to go to the previous directory which I was in when changing directory with the cd command? For example, I'm in /opt/soft/bin and I cd into /etc/squid3 and I want ...
3
votes
1answer
38 views

Redirection with nested commands

I am running a $command, in a instance of a screen, as a different user. It's run by the equivalent of this command (more detailed at bottom): su $USERNAME -c "screen -dmS $SCREENNAME $COMMAND" and ...
9
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2answers
366 views

When is it important to write portable scripts?

Most code I write is in PHP. I have recently started learning shell scripting. Most of the resources and tutorials that I've come across are specific to Bash. Some warn about bashisms and some don't. ...
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2answers
156 views

status check for sleep command

I have run sleep command in background as follow , How can I know the status of execution ..? Command sleep 2d ; find /home/disk1/ -exec touch {} \; & How can I know that its executed for 1 ...
0
votes
1answer
84 views

How could I include a variable in a here document?

I am trying to use a user-defined global variable in a cat <<eof>> filename situation, but it's not working. I found what I want in simple cat << eof examples on this forum, which ...
3
votes
3answers
5k views

Test if telnet port is active within a shell script

I am trying to create a script to test whether it is possible to login via telnet. I do not want to really log in; therefore, expect is not needed. I just want to see if I am able to get a login ...
42
votes
4answers
72k views

How to suspend and bring a background process to foreground

I have a process originally running in the foreground. I suspended by Ctrl+Z, and then resume its running in the background by bg <jobid>. I wonder how to suspend a process running in the ...
2
votes
2answers
26 views

variable substitution in CLI and for loops

I am pretty sure this has been asked already in some form, I just cannot come up with a good find to search it. I want to have a script that do things N times and to which I can pass as a variable ...
2
votes
1answer
358 views

Is there any way to check email sent success acknowledgement?

I need to send the generated CSV files on regular intervals using script. I am using UUENCODE and mailx for the same. But i need to know that is there any method/way to know that email sent ...
31
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6answers
3k views

When do you use brace expansion?

I understand what brace expansion is, but I don't know how best to use it. When do you use it? Please teach me some convenient and remarkable examples if you have your own tip.
1
vote
1answer
98 views

using script function rather than keyboard input

I'm writing a shell script to change a user's password. I tried to use the passwd command, but that command always asks for the old and new passwords to be typed; it won't accept them from my script. ...
1
vote
1answer
86 views

How to remove message when opening terminal/solve?

I am receiving the below message whenever I open the terminal. Repository u'ffmulticonverter_stable': Error parsing config: Error parsing "baseurl = u'ppa:ffmulticonverter/stable'": URL must be ...
4
votes
1answer
243 views

How do I come by this pty and what can I do with it?

It seems that a simple shell redirect from /dev/ptmx gets me a new pseudo-terminal. $ ls /dev/pts; ls /dev/pts </dev/ptmx 0 1 2 ptmx 0 1 2 3 ptmx It disappears as soon as the process that ...
0
votes
1answer
42 views

unable to read the output to run the next command [closed]

When this script is executed I get the PID. Now I want to read the output "PID" and run the next command in this way: ps -ef | grep -i PID ps -ef | grep -i PID while read -r -u10 server port ...
2
votes
3answers
56 views

How to enter the condition to check 0 or more than 0 in case

I am trying to use case to run this function if [[ $input -gt 0 || $input -eq 0 ]]; Is it possible to put in case to test the input for greater than 0 or equal to 0, or even 0 and less than 0, in ...
5
votes
2answers
445 views

If any spawned child processes fail, kill all and exit

In my script I split up a data set into input_aa, input_ab, etc. Then, I run each through the same Python script, as such: # Execute program on each split file for part in input_*; do python3 ...
2
votes
0answers
97 views

“Restart” a process in the same terminal?

I put "restart" in quotes because the following question on SO illustrates what I'm trying to do: http://stackoverflow.com/questions/27957091/restarting-a-process-in-the-same-linux-terminal I'm ...
2
votes
2answers
280 views

Print file name extension using -exec in find

I am playing around with -exec flag of find command. I am trying to use the flag to print the extension name of files, using a fairly new Linux distribution release. Starting simple, this works: ...
3
votes
1answer
118 views

Can lightdm/gnome/compiz use bash instead of sh?

On my Ubuntu 12.04 logging in is handled by the lightdm which starts a gnome-session for the user which starts a compiz instance which then starts the applications the user clicks on. Somewhere in ...
5
votes
2answers
282 views

Two-words argument in shell script

I have a problem with a shell script. It is supposed to read arguments: index, date, time1 (the beginning of the interval), time2 (the end of the interval). It should count how many times the ...
1
vote
3answers
281 views

How do I make an output for grep fail?

I am using if-else statement to search for keywords and displaying the results in the terminal, here's an example of my code. read finding if ["$finding" != "" ]; then grep $finding ...
5
votes
2answers
70 views

Introduction of env --null

I have tried to extract environment variables in a Python process with help of env --null, which works even for environment variables containing newline character. But on some machines I have ...
1
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0answers
28 views

If I cancel when prompted for my Git password, I can no longer see anything I type, until I log back in [duplicate]

Everything still works (typing "exit", for instance, exits), but I can't see anything I type. There's not "funny characters", just nothing. Even re-running git and entering the password properly ...
1
vote
1answer
89 views

Why doesn't my function work with spaces? (cd, dirname) [duplicate]

I have had this function I use it very often and it works fine. Here it is: cdx () { cd `dirname $1` ; } However, this does not work with spaces. When I use it like this for example cdx ...
2
votes
1answer
195 views

Export path with space in directory name [duplicate]

I have a path "/third/party/city of las vegas" when cd the path I use "/third/party/city of las vegas". In .profile file I have exported the path to a variable as follows export ...
18
votes
6answers
2k views

Is there another simple way to append line to end of file other than `>>`?

Recently I'm echoing short sentences to a tree_hole file. I was using echo 'something' >> tree_hole to do this job. But I was always worried of what if I mis-input of > instead of >>, ...