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)

0
votes
1answer
18 views

What is the most Unix-y way to handle stdout for a backup command that might fail?

I am writing a utility/script (in Python, as it happens) to run on Linux, which backs up data from a remote server, and outputs to stdout. At the moment, I run this script on the hour from cron, and ...
4
votes
5answers
236 views

How do you interact with a file named “!!”? [duplicate]

Out of rage, I quit vim by using :wq!!!. This created a file named !!. Given that !! references the previous command, attempting to interact with it yields interesting results. I tried rm ./!! and ...
0
votes
2answers
21 views

Root to the Minimal

I am building a script to automate and minimize access to root. I am going to try do it via SSH. I am currently having an issue using sed to replace UID and GID 0 shell to /sbin/nologin. Why am I ...
4
votes
1answer
486 views

Which 2-letter POSIX command is different from all the others?

I was interviewed for an internship and I got the same question as this one: http://www.glassdoor.com/Interview/Which-2-letter-POSIX-command-is-different-from-all-the-others-QTN_498236.htm The ...
2
votes
1answer
32 views

How do I securely download files in shell scripting?

I am writing some shell scripts to automatically download software packages off my server and set them up on customer servers. At some point within the script, the download command is wget ...
0
votes
0answers
19 views

How to zip only files under multiple subdirectories?

This may be sounding familiar, but its different. I want a command in terminal that does this - I have a folder working and its structure is something like this - working/ 100/ 1/ 2/ ...
2
votes
2answers
1k views

Using sudoers to allow php to run command

I am trying to get my php page to run this command: shell_exec("sudo /home/xbian/433Utils/RPi_utils/codesend {$num}"); So I added this entry to my sudoers file with visudo: www-data ALL=NOPASSWD: ...
2
votes
2answers
41 views

Export Command History into a Shell Script

Often I have complicated installation procedures to follow, like having to build dependencies for buildtools, to build dependencies for the application I wish to install from source. Once I have done ...
13
votes
3answers
788 views

Any reason to use or teach `…` substition for new development?

It is my understanding that the more modern $(...) command substitution syntax is preferred over the old `-based syntax, due to easier and less error-prone nesting and escaping syntax. Further, it ...
0
votes
1answer
13 views

Insert space at specified position in a file

I have this sample file: 234234|111||J1X0H8|SERP||R|D|666|M 234235|222||J1X0N5|SERP||C||555|M For each line, I need to insert a space after the 3rd character of the 4th column, like so: ...
11
votes
3answers
2k views

Can't indent heredoc to match nesting's indent

If there's a "First World Problems" for scripting, this would be it. I have the following code in a script I'm updating: if [ $diffLines -eq 1 ]; then dateLastChanged=$(stat --format '%y' ...
11
votes
5answers
1k views

Shell: “Display all 2588 possibilities?”

So, I was moving my laptop around (and I have the bad habit of setting things on the keyboard...) and I woke up to discover this: $ Display all 2588 possibilities? (y or n) What command would ...
-4
votes
2answers
45 views

How do I print all env vars beginning with the letter 'T'?

This was an exercise for a course I'm on and I got really stuck at frustrated. I think my main problem is I keep putting the ">>" the wrong way round and then getting stuck in an editor which I don't ...
1
vote
2answers
51 views

readlink -f not working on multiple files

I tried to run readlink -f on multiple files by using wildcard "*", but it evaluates other files as operand Command readlink -f *log Output (desired) /home/trail_1.log /home/trail_2.log Am I ...
1
vote
1answer
36 views

Is there a way to change the number of processors a program sees?

Is there any way I can trick a program into thinking the system has fewer processors? To explain: I am debugging a program that creates as many threads as it has processors, using ...
67
votes
6answers
39k views

Allow setuid on shell scripts

The setuid permission bit tells Linux to run a program with the effective user id of the owner instead of the executor: > cat setuid-test.c #include <stdio.h> #include <unistd.h> int ...
0
votes
2answers
22 views

redirect output from interface?

I am echoing an AT command to a modem interface (/dev/ttyUSB3) and the command runs successfully. For instance the below command works and has an output of OK: echo -e "ATZ\r" > /dev/ttyUSB3 I ...
0
votes
2answers
49 views

Untar and gzip from multiple sub directories

I have a directory which consists of multiple sub-directories. Each subdirectory has a tar.gz file which on untar gives two files namely R1.fastq and R2.fastq. I want to untar the tar file and ...
17
votes
5answers
19k views

Shell: How to read the bytes of a binary file and print as hexadecimal?

In shell, how can I read the bytes of a binary file I have, and print the output as hexadecimal numbers?
1
vote
1answer
28 views

Save and restore terminal tabs with custom tabs title

I have a Terminal window with a dozen named tabs open *(gnome-terminal) I would like to save the current configuration and have it restored with names and directories. Is there a way to do this? I've ...
1
vote
1answer
39 views

Read a character from an x-y coordinate on the screen

Is there a way in bash to read a character from an x-y coordinate on the screen? This command would be something similar to cget 12 30 which would return the character at the 12th row and 30th ...
0
votes
0answers
30 views

Pass a function arguments?

How would you make a function that gets arguments? function arg_example { arg "c" # This is imaginary but it would return 'true' if it found the argument -c. did_find_arg=$? # Get the ...
0
votes
1answer
28 views

Opening a socket in Kali Linux using bash scripts

I know how to open a TCP or UDP socket in Ubuntu, with the following command : exec 3<>/dev/tcp/google.com/80 for example: we can open a TCP socket on port 80, but in Kali Linux there's no ...
9
votes
5answers
738 views

How to get the last N files in a directory?

I have many files that are ordered by file name in a directory. I wish to copy the final N (say, N=4) files to my home directory. How should I do it? cp ./<the final 4 files> ~/
0
votes
2answers
19 views

The best way to add Unix Shell variables to CURL GET request

Let’s say I use curl –X GET command with the following link: “$WEBSITE_URL/ACTION_NAME/ACTION1;id=$ID?Command=TEST&id1=$ID1&id2=$ID2&id3=$ID3” As you can see, there are some $variables ...
1
vote
2answers
46 views

BASH: Command not running, special character '�' suddenly appeared (Ubuntu)

When I erroneously type 'ñ' (expecting to type any command) and then remove it and type the correct letter, the output returns the command with a special character attached �, obviously the shell ...
11
votes
3answers
582 views

Terminal vs bash? [duplicate]

I'm on a Mac but I think this is generally Unix-applicable. I'm in the process of learning shell scripting and there's something I seem to be missing. When I'm in the ordinary terminal, I can use ...
19
votes
6answers
1k views

Do we have more history for cd?

cd - can move to the last visited directory. Can we visit more history other than the last one?
8
votes
2answers
413 views

Run another command before running the command the user wants to run

Let's say I want to modify the original behavior of the ls tool this way: $ ls Hello World file1 file2 ... How can I do this? When running ls I would like to run another command let's say echo ...
3
votes
2answers
108 views

Assign specific line from a variable to another variable

I would like to take a specific line from a variable to another variable. I tried this but it doesn't work: c="1.apple 2.banna 3.peach" read "Please choose fruit [1-3]:" t a=$c | awk "NR==$t" echo ...
1
vote
2answers
175 views

Why does “grep '.*[s]' file” work and “grep .*[s] file” doesn't?

Comparing grep '.*[s]' file with grep .*[s] file Why do you need quotation marks to let this work properly? In the second case, grep seems trying to inspect every file with a period.
0
votes
2answers
14 views

tcpdump filter expression breaks via adb

I installed tcpdump on my Android tablet and am running commands from a root adb shell. I'm working from the tcpdump man page examples, specifically this one: To print all IPv4 HTTP packets to and ...
0
votes
1answer
144 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 ...
3
votes
3answers
149 views

Piping a script with “read” to bash

I need to run a script by piping it through bash with wget(rather than running it directly with bash). $ wget -O - http://example.com/my-script.sh | bash It's not working because my script has read ...
1
vote
1answer
13 views

Understanding directory symlinks traversals and the parent directory

Let's say you have directories /dir1 and /dir2/linked, where the later is a symlink to the former. When you cd to linked and pwd, you get the output /dir2/linked. If you then cd .., you'll be put on ...
2
votes
1answer
72 views

bash find: get directory of found file

I have a parent folder named "parent_folder" with a lot of subfolders, in these subfolders is a file named "foo.mp4". I can find these files easily by doing this: mymacbook:parent_folder username$ ...
0
votes
1answer
31 views

UnixWare 7 fails to pass variable to Linux

I'm new to Bash and I have a problem that find difficult to solve, may be easy for some. I have a really old SCO UnixWare 7 system with no SSH only RSH available. SCO doesn't exist anymore , I ...
0
votes
4answers
106 views

How do i change the case (upper and lower case) of strings in my variable?

"Enter test: " read test if [[ $test == "a" ]]; then echo "worked" else echo "failed" fi It's a simple illustration of test i'm doing, but if i enter "A", it will fail, is there anything i ...
3
votes
2answers
45 views

Why alias inside function does not work?

See the code below: a()(alias x=echo\ hi;type x;alias;x);a I have an alias inside a function, I do not want to change the external environment (that is why I am using () instead of {}), even the ...
1
vote
1answer
41 views

Equivalent of Java's String.getBytes() in Unix Shell (Cygwin)

Let's say I convert my string into byte array. byte[] byte sUserID.getBytes(“UTF-8”); //Convert User ID String to byte array Now I need to write a script on Shell that will have exactly the ...
0
votes
1answer
19 views

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
votes
2answers
198 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
votes
2answers
59 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 ...
-2
votes
0answers
26 views

How to create symbolic link to a directory with custom name

I want to create a sym link from the source name TEST to the destination name NAME if i give ln -s TEST /NAME - its going to create the Folder in the /NAME with TEST name but i want to get as NAME ...
1
vote
2answers
129 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 ...
0
votes
0answers
66 views

How to give shell access within chroot environment having different home directories? [closed]

I want to give limited bash shell commands or we can say shell access to the chrooted users but after configuration users are able to do sftp only. I have also found that it is possible by providing ...
1
vote
1answer
25 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 ...
11
votes
2answers
9k views

how to output text to both screen and file inside a shell script?

Currently I have a shell script which logs messages to a log file like this: log_file="/some/dir/log_file.log" echo "some text" >> $log_file do_some_command echo "more text" >> $log_file ...
18
votes
10answers
7k views

Object-oriented shell for *nix

Preface: I love bash and have no intention of starting any sort of argument or holy-war, and hopefully this is not an extremely naive question. This question is somewhat related to this post on ...
-2
votes
2answers
32 views

What is a simple example where the use of the command line is unavoidable or better? [closed]

I want to see a simple example that motivates the use of the Linux command line. Like I want to see an example where the use of the command line will do it in seconds and on GUI , it will take you ...