Questions tagged [shell]
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, …). For shell scripts with errors, please check them in http://shellcheck.net before posting here.
11,937
questions
0
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1
answer
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Create user with shell access but no GUI login
I need to create a User that can interact with shell it has home directory but no GUI login. I have looked at many articles on this. but I am pretty confused as the correct process useradd --system ...
- 1
2
votes
1
answer
58
views
Linux (Bash): Are Login Scripts With Exit Conditions Or Exec Commands Possible?
I want to run a login script for all users, that checks whether the user is an administrator and, if so, offers the option of a host login, or launches a systemd-nspawn container by default - that way ...
- 21
1
vote
5
answers
135
views
How can I convert a reverse IP address to IP?
I want to convert a list of reverse DNS IP addresses to normal format.
i.e.
Convert 43.201.125.10.in-addr.arpa to 10.125.201.43
Is it feasible?
6
votes
2
answers
1k
views
Why xargs does not process the last argument?
Observe:
mark@L-R910LPKW:~$ echo a b | xargs -d' ' -I{} bash -c 'echo {} 1'
a 1
b
bash: line 2: 1: command not found
mark@L-R910LPKW:~$
What is going on?
- 387
-3
votes
1
answer
126
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Im trying to run a shell script but I keep getting If: expression syntax. How to I get rid of it
Good afternoon, I'm trying to run my code for assignment 4 but I keep getting an expression syntax error, can you tell me why?
#!/bin/sh
if [ "$#" -ne 1 ] then
echo "Usage: ...
- 1
12
votes
2
answers
3k
views
Does ssh run commands (rather than shell itself) in a login shell?
According to man sshd:
LOGIN PROCESS
When a user successfully logs in, sshd does the following:
<...>
9. Runs user's shell or command. All commands are run under ...
- 567
0
votes
1
answer
3k
views
How to extract stdout of command as variable in ansible playbook
I am trying to install docker credential store with pass on a VM using Ansible
here is the part of the credential store's code in the playbook.yaml
However, the problem is I try to export the gpg key ...
- 31
2
votes
1
answer
34
views
How to concatenate files and give another name to output based on the match from another file?
I have a directory data in which there are several fastqs like below:
SRR13456784_1.fastq
SRR13456784_2.fastq
SRR13456784_3.fastq
SRR13456785_1.fastq
SRR13456785_2.fastq
SRR13456785_3.fastq
...
- 351
1
vote
1
answer
64
views
Does POSIX sh require expanding $! in order to keep a reference to the child process?
Spec
According to this online POSIX Spec, in Shell & Utilities, Shell Command Language, Section 2.9.3 Lists has the following to say about Asynchronous Lists:
When an element of an asynchronous ...
- 484
0
votes
1
answer
161
views
How to track all signal in 'trap'?
Can I test keyboard shortcuts and some kill commands with a script and know which signal is caught by trap?
- 32.2k
0
votes
3
answers
95
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Handle parentheses in this xargs multi-command
I suspect the following has been answered already but I don't know the terminology for the issue I'm having well enough to find an existing answer.
I'm working on a command to go through a list of ...
- 133
1
vote
1
answer
31
views
How to Check Numlock State of Virtual TTYs Without Elevated Privileges?
I am trying to get the numlock states of multiple virtual TTYs. But my normal user account doesn't have read permission for some of them.
$ for tty in /dev/tty{1..6}; do setleds < ${tty} | grep &...
- 225
0
votes
1
answer
46
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ls -F/--classify marks every file as an executable
ls -F classifies ALL files on my mounted partitions as an executable (it appends an asterisk to the end of the file name).
The same command performs correctly in other places like my home folder, so I ...
- 113
0
votes
2
answers
88
views
How is output passed as input in pipes?
I am trying to understand how pipes | work; in particular, in what way the output from the left command is passed as the input to the right command. Is the output from the left command treated as a ...
0
votes
4
answers
526
views
Shell script to list all files in a folder on a single line
I have this folder structure:
/Brand/ProductCode01
/Brand/ProductCode02
Each ProductCode## folder contains many JPG files, like
image01.jpg, image02.jpg and so on
I need to create a file that ...
0
votes
0
answers
46
views
Compress list of files as their shortest exclusive glob
How can I convert a list of files to the minimum-length glob that expands to those files and no others?
E.g. in a directory
root
├── one
└── two
Then the list root/one:root/two can be converted to ...
- 807
0
votes
0
answers
30
views
'-bash: line 1: rescanscsi: command not found' error even though script location is in PATH and other script runs fine from same folder [duplicate]
I'm new to linux, trying to switch over from Windows, and I could really use some help. This is actually my first time using a forum such as this so please forgive any errors I make.
I'm using Linux ...
-2
votes
1
answer
41
views
confusing concepts of environment variables, shell variables, shell function, userdefined var, command aliases [closed]
I am studying about environment in linux, and these words confuses me.
isn't there just system defined variables generated by kernel and user defined variables which is assume to be lower case?? ...
0
votes
0
answers
300
views
Use shell command to set env variable in Dockerfile
I am trying ot set up a custom redis alpine image and I would like to set the private IP that get assigned to the instance as an environment variable. In order to do so, I am using the following ...
2
votes
2
answers
106
views
how to specify multiple inputs for a command in shell script
I have several fastq files per sample and all of them should be provided at once as an input (as they all belong to one sample, they should NOT be treated independently like in a for loop, as they are ...
- 1,016
0
votes
1
answer
51
views
Problem with bash builtin bind and escaping
I'm trying to add a history fuzzyfind hotkey to my bash shell. However, my intended command gets cut in the middle:
[april@Capybara-2:~]$ cat ~/.bashrc
bind "\"\C-r\": \"\$(...
- 137
1
vote
1
answer
68
views
Remove entire folder when grep find no files with a match inside the folder
I have thousands of folders with a single html file in each folder. I want to remove the entire folder if grep find no match to example.com in the html file.
I know how to remove the non matching file....
- 359
5
votes
2
answers
580
views
touch command not able to create file in write-permitted directory
This is my user
$ id
uid=1000(pzk) gid=1000(pzk) groups=1000(pzk)
This is my directory structure
$ ls -tlrh
total 12K
d-w--w--w- 2 root root 4.0K Apr 13 10:53 write-for-everyone
dr--r--r-- 2 root ...
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1
vote
0
answers
323
views
Merge set x (xtrace) and v (verbose)
How to merge set -x and set -v in ash? (or set -v with a prefix)
In other words, echo back command upon running.
The DEBUG signal does not exist in ash: DEBUG: invalid signal specification.
set -x
$ ...
- 376
0
votes
0
answers
21
views
Insert into the shell a filepath used from a previous command [duplicate]
I have a series of commands like
$ touch path/to/file.cc
$ less path/to/file.cc
...
and in the second command I'd like to automatically insert the path used in the previous command. Is there a way to ...
- 314
0
votes
0
answers
84
views
Running a local script on remote server over ssh with sudo privileges
I have a script script.sh on local machine which I want to execute on remote server with sudo permissions. I am logging in to remote server through SSH and executing the script using the below command
...
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0
votes
1
answer
75
views
What is the number inside the parenthesis on a Linux command? [duplicate]
What is 1? What is 3? What are the numbers called and is there a full list with explanations?
$ whatis nvim
nvim (1) - edit text
$ whatis printf
printf (3) - formatted output ...
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0
votes
0
answers
86
views
Midnight Commander: shell link connection not show dirs
Everything works fine when the target computer is windows 10 with cygwin and openssh 5.9p1-1 (libopenssl098 0.9.8t-1) [computer1].
After upgrading cygwin with openssh 1.1.1t-1 (libssl1.1 1.1.1t-1) [...
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0
votes
0
answers
120
views
Limit the total CPU usage for the entire system?
I'm running a Chrome instance on a NAT VPS. Being a NAT VPS it has some restrictions such not not allowing a 15min average load greater than 1. However, just starting and going to a few webpages ...
- 35
7
votes
1
answer
1k
views
mv: rename <oldname> to <newname>/<oldname>: Invalid argument
On my TrueNAS (FreeBSD 13.1) server I have a directory named OldHDD which I want to rename, but I get an error:
% mv OldHDD oldhdd
mv: rename OldHDD to oldhdd/OldHDD: Invalid argument
I have tried ...
3
votes
2
answers
693
views
Race condition not seen while two scripts write to a same file
I have two scripts running parallelly and they are echoing to the same file. One script is echoing +++++++++++++++ to the file while the other script is echoing =========== to the file.
Below is the ...
- 101
6
votes
2
answers
806
views
bg command not sending process to background
After pausing the process with ctrl-z, I attempted to send it to background with bg command. Unfortunately, the process isn't sent to the background, and reappear to be running foreground. Then, I do ...
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1
answer
103
views
How was a shell like when operating systems didn't had a GUI? [closed]
I understand the concepts of terminal, console, shell and their differences. I know a shell today is an interpreter that communicates with the OS kernel to perform some actions and does it through ...
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0
votes
0
answers
73
views
How to cp all files within /var/log without using sudo
This is in shell script. I want to create a directory copy of /var/log while preserving directory structure (so not tar).
I do this by making a directory and using cp -R /var/log cpdir However, some ...
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0
votes
0
answers
25
views
bash lost string begin if "-e" are first symbols [duplicate]
I need echo this construction and cannot use additional quotes
#!/bin/bash
set -x
export jaz="-e test \
-e test2 \
-e test3
"
echo $jaz
result is
tuy$ sh test.sh
+...
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1
vote
1
answer
87
views
zsh completion: complete --options for custom script
I have zsh completion rule for custom script. My script can take zero or more options (starting with -) and zero or more arbitrary strings (patterns):
_arguments -S : \
'--foo' \
'--bar' \
...
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2
votes
1
answer
196
views
How to parse positional parameters of Bash script when using "Bash Strict Mode"?
Bash Strict Mode is defined as follows:
#!/bin/bash
set -euo pipefail
IFS=$'\n\t'
http://redsymbol.net/articles/unofficial-bash-strict-mode/
Consider the following parsing of positional parameters in ...
- 4,073
0
votes
2
answers
75
views
Linux - Live List of Running Processes
Is there a way to get a list of all running processes that will auto update when new processes start running or remove themselves if they have stopped running?
Example:
ps gives me a list of processes ...
0
votes
1
answer
266
views
Shell scripting, reading a list from tt file, use as variable, use the variable to run python scripts in a foor loop
I am trying to run a shell script where it reads the variables from a txt file, uses that variable in a for loop to run python file.
The code reads a txt file where at least there are 100 variable ...
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0
votes
1
answer
72
views
colorizing commands vs arguments in output of shell
When working with make/cmake scripts you often have to use VERBOSE=1 and look at all the commands run. This is what I do a lot, and its utterly straining for someone just looking for the origin of ...
4
votes
2
answers
1k
views
How to pin a package version with `nix-shell`?
From what I understand, I can use a given version of Nix packages using the -I flag. But I would like to know if it is possible within a single shell.nix conf to have something like:
git v2.1.2
htop ...
- 41
0
votes
0
answers
75
views
Get WID from PID using Gnome-terminal
For getting WID from PID, I use xdotool search -pid PID. In some terminals, it works correctly - outputs one number (WID of window), but in Gnome-terminal, besides WID, it outputs some other IDs. The ...
- 1
3
votes
1
answer
180
views
Launch process with limited capabilities on minimal Busybox-based system
In a minimal Busybox-based Linux system with access to the root user, how can one launch a process with a specific limited set of Linux capabilities(7) without requiring any tools beyond busybox?
- 1,913
1
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1
answer
67
views
optipng in parallel using shell
I would like to run optipng in parallel with my 8-thread CPU using the shell.
I know the program itself is not multicore optimized, the only way will be to run 8 files with it.
I have 500+ PNG images ...
- 27.8k
0
votes
1
answer
481
views
Trapping SIGINT so that the process kills itself
So section 5 from here made sense to me and I wanted to implement it. I have this bash script
#!/usr/bin/env bash
cp aux.sh aux.sh.bak
cleanup() {
cp aux.sh.bak aux.sh
rm -rf aux.sh.bak
}
...
- 103
0
votes
1
answer
38
views
What is the EPS1 environment variable used in zsh prompts?
Many zsh configs floating around the internet that set the right-hand prompt RPS1 append the value of EPS1 to the end, but I have found no documentation anywhere of what EPS1 might contain. On my ...
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votes
2
answers
161
views
Output date into specific column using bash
I want to output the date into a csv column using a bash script ignoring the header. I have this but it only gives the day of the week abbreviated and not does not place it in a specific column:
date |...
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votes
1
answer
315
views
Does running exec command preserves environment variables of the calling shell? If so, why?
From my understanding exec command replaces the calling shell program with the command without forking a child process. Also if I understand correctly exported variables are the ones that are passed ...
7
votes
2
answers
1k
views
How do I keep a dash shell script running despite any error?
I have a dash shell script that is intended to run to the end of file:
#!/usr/bin/dash
# File b_shell
. a_nonexistent_file
echo "I want to print this line despite any previous error."
...
- 171
0
votes
1
answer
81
views
Where should I put my personal shell script in terms of safety?
I am learning sh to make some customized function. I am looking for a safety location for the personal script, since I check from stack exchange, some say that put personal script under ~/bin may ...
