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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23 views

Command Playlist like music.

So that idea has been in my head for a while, I often find myself launching a command and then wanting to launch another one after the one in progress finishes. The issue is that I have to monitor ...
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3answers
49 views

Comparing integers: arithmetic expression or conditional expression

In Bash, two integers can be compared using conditional expression arg1 OP arg2 OP is one of ‘-eq’, ‘-ne’, ‘-lt’, ‘-le’, ‘-gt’, or ‘-ge’. These arithmetic binary operators return true if ...
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2answers
49 views

What's the difference between using shell command (e.g. foo) directly and using $(foo)?

I get confused about using command directly and using $(foo). I'm using Mac, I try to list apps which is install by brew cask(a package manager), and echo each app. I have two short Shell scripts, ...
3
votes
1answer
146 views

Variables of integer type in Bash?

There are two ways to define and use variables of integer type in Bash declare -i a new variable use a variable in an arithmetic expression, without declaring it. My questions: What are the ...
2
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1answer
56 views

How can I check if a shell is login/interactive/batch in fish?

I want to be able to check if a fish shell is being run in login, interactive, or batch mode, and this question only discusses bash.
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1answer
34 views

Create HISTFILE in subshell

Here is my HISTFILE: $ echo $HISTFILE /home/Steven/.bash_history I can create it by using exit: $ [ -e $HISTFILE ]; echo $? 1 $ exit $ [ -e $HISTFILE ]; echo $? 0 However if I exit a subshell, ...
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2answers
18 views

Deleting lines by matching 3rd and 4th character only

I am running a script that fetches me the data as given below, 1400d2b8 1f4d1e2507 1200781e As you can see the 3rd and 4th character is 0 in line 1 and line 3. I am trying to write a single line ...
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3answers
35 views

How to pass array to bash shell script?

How do I pass an array as a variable from a first bash shell script to a second script. first.sh #!/bin/bash AR=('foo' 'bar' 'baz' 'bat') sh second.sh "$AR" # foo sh second.sh "${AR[@]}" # foo ...
3
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3answers
194 views

POSIX compliance of the cd program?

Is globbing and shell expansion same thing? I'm learning C by writing a custom shell and I'm also learning POSIX. Now I wonder if it is POSIX compliance that cd - takes you back and that ~ means home ...
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1answer
39 views

Is a string an arithmetic expression?

In Bash, I use a string where an arithmetic expression is expected: $ (( hello )) $ echo $? 1 $ echo $(( hello )) 0 $ let aaa=hello $ echo $? 1 $ echo $aaa 0 There is no error reported. So is a ...
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0answers
13 views

TZ variable: strange behaviour using Etc/GMT+x? [duplicate]

Could anyone explain why the following commands return different results? TZ="Australia/Sydney" date TZ="Etc/GMT+10" date Sydney is 10 hours ahead of GMT, so the results should be equal, but I get ...
2
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1answer
25 views

Bash shell script program that prompts for and reads two integers from the user.

Okay, so I been trying to figure this problem for a while and I'm coming up with errors left and right. This is my first time trying to learn the basics. So any advice would be helpful! Problem: I'm ...
2
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2answers
55 views

Accessing array index variable from bash shell script loop?

I want to access the array index variable while looping thru an array in my bash shell script. myscript.sh #!/bin/bash AR=('foo' 'bar' 'baz' 'bat') for i in ${AR[*]}; do echo $i done The result ...
0
votes
2answers
73 views

Error when eval a for-loop

I am writing a script which accepts two arguments: #! /bin/bash eval for i in {$1..$2}; do echo $i; done I run it like: $ ./myscript 0002 0010 syntax error near unexpected token `do' Why is ...
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votes
1answer
39 views

What is the purpose of eval? [duplicate]

What is the purpose of running a command with eval? What kinds of commands can eval run? I find it can run builtin command, external executable command, pipeline, script. Can it run all kinds of ...
1
vote
2answers
50 views

Grep command using contents of a heredoc

I'm creating a script to update a remote computer and I want to know if any user is using the computer before I update. I have a list of users and I created a heredoc with all of them. The command I'm ...
7
votes
2answers
223 views

How to avoid space after bash variable in string?

I have a variable for color. I use it to set color to strings, by evaluating it inside the string. However, I need to include space after the name(so that the name doesn't contain part of the text). ...
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2answers
20 views

How to use the result from last calculation in a new calculation in wcalc?

In wcalc how can I do something like -> 1+2 = 3 -> X+1 = 4 where X equals the result of the last calculation (that is 3)?
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1answer
25 views

Debian : Setting path for Node with root accessible globally

I have downloaded NodeJS setup and have it inside at /home/deploy/nodejs. I am trying to set its path, but it's not working out. I am logged in as root, and I would like to access nodejs and npm ...
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3answers
66 views

I want to copy a remote txt file via SSH, but without using root access

I want to copy my hosts to remote /etc/hosts but it doesn't work. I know root SSH access makes things easier, but IMHO root SSH access is a little dangerous. cat /etc/hosts|ssh samba2 "sudo su -c ...
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1answer
25 views

setting umask for directories and files

Is it possible to create an umask , which will result in newly created files and directorties to have the same access rights ? e.g both of them to have for example rwxrwrw Directories starts with ...
2
votes
1answer
57 views

Systemd: How to start/stop Python script that should run in background, inside Virtualenv

On my Raspbian machine, I want a successful OpenVPN connection to my VPN provider to initiate a Python script, that persistently should run in the background as long as the VPN connection is active. ...
1
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0answers
29 views

Deleted file being written to by running process, can I recreate it? [duplicate]

I've started a long running process with nohup and redirected it's output to a log file Example: nohup ./bin/zkServer.sh start-foreground > /usr/local/myuser/logs/zkout.log 2>&1 & I ...
2
votes
1answer
33 views

grep/awk specific lines based on specific fields; using ksh variable with awk

I have this input file: file_in.txt (delimited by pipe) 3345:tyg|rty|27|0|0|ty6|{89|io|}62|0 3346:tyg|rtyuio|63|0|1|ty6|{89|gh|}45|0 3347:tyu|ray|24|0|0|ty6|{89|uh|}27|0 ...
3
votes
1answer
35 views

integer expression expected

I have the following script that is trying to match and IP address with a value in a file #!/usr/bin/env bash #To find the IP via ping ping=$(ping federicolivieri.noip.me -c 1) #To cut the result ...
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2answers
49 views

python virtual environment

I have to install python package locally/globally on a machine using pip, so for I do not want to install pip on local machine. I can successfully create a new virtual environment using easy_install ...
1
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2answers
36 views

Get full directory of $file

My first shell script #!/bin/bash echo "Input your file" read $file path=(readlink -f $file) echo "$USER, $path" >> scriptlog.txt it said missing operand. How can I fix it?
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2answers
49 views

I want search for a string and to pull all the lines between two patterns [duplicate]

I want search for a string and to pull all the lines between two patterns(including the pattern). START#1 Name S 101 Frankfurt_1_1 19 A+ Street END START#2 Name B 104 Berlin 20 A+ ...
2
votes
2answers
37 views

GNU Parallel: immediately display job stderr/stdout one-at-a-time by jobs order

I know that GNU Parallel buffers std/stderr because it doesn't want jobs output to be mangled, but if I run my jobs with parallel do_something ::: task_1 task_2 task_3, is there anyway for task_1's ...
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0answers
32 views

How can I find and zip all resource bundle properties with shell

I am totally new to Unix and shell programing. Here is the requirement: There are bunch of Java resource bundle properties scattered in a folder and it's sub-folders. And to make problem simple, ...
4
votes
1answer
75 views

How Do I Remove Duplicate Words With Suffixes?

How do I compare a list of unsorted words of variable length and remove duplicate words that have a suffix? Example word list: iron curl curled railroad curler ...
1
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2answers
38 views

What sets the $SHELL environment variable?

Where is the environment variable $SHELL first set on a UNIX system? How can I find and print all of this type of default settings of my terminal?
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0answers
20 views

search insert and replace [duplicate]

I want to search each record (records are defined by blank lines) in a file for the pattern NAME#AAAA. If it matches, then insert an # in front of the record's AGE line and move that line to the top ...
0
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2answers
23 views

Why does ls still show the file excluded via GLOBIGNORE?

File missing with echo but present with ls -a. Why? bojan@hyperion:~$ touch .ignoramus bojan@localhost:~$ ls -al | grep ignor -rw-rw-r-- 1 bojan bojan 0 Apr 19 19:05 .ignoramus ...
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2answers
24 views

Supressing the original output

What or how does shell supress the output while using pipes in a script? Lets say we have code cat file | wc -l only the number of lines gets printed. Where does shell store the content of the file ...
0
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0answers
16 views

I want to search for a pattern in a file. If the pattern matches, it should check for second pattern and replace it with another pattern file [duplicate]

I want to search for a pattern in a file. If the pattern matches, it should check for second pattern and replace it with another pattern INPUT FILE Name#AAAAA std 1 sec c age 5 Name#BBBB std 2 ...
0
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0answers
18 views

Possibility to write some words in different color in log file [duplicate]

Is there a possibility to colorize words in a log file? I want to have the word ERROR in my logfile always in red, to see it more easily. I watch it with the tail function: tail -f -n 500 ...
3
votes
1answer
38 views

How to revoke access for a particular user?

How can I revoke all access (r,w,x) for a particular user to a file or directory tree (while still giving read permission to others)? Does setfacl with mask allow this ?
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votes
1answer
49 views

Is the value of a variable lost after a command is executed?

There is a functional difference between using: n=$1 shift And using: n=$1; shift in bash and zsh: the value of n is lost after the shift is executed in the first example. But both have the ...
2
votes
1answer
57 views

bash: cannot create temp file for here-document: No space left on device

one day I was doing some stuff and I might have changed something which I shouldn't (I was working on the /etc/network/interfaces file). By the way, this is my OS: $ uname -a Linux ribas ...
0
votes
4answers
96 views

How to run subshell commands over SSH?

I have a cluster of computers which are connected via passwordless SSH and I have written a utility which runs a command over the entire cluster. The way it does it is by picking up machines present ...
3
votes
3answers
93 views

How can I test if a file in /root exists without su to root?

My OS is Ubuntu 14.04 LTS. I got a file /root/1.txt, and logged in with 'yu', who doesn't have read permission on this file. When I use the code if [ -e /root/1.txt ] , it returns false. I know I can ...
2
votes
1answer
43 views

Change to a directory containing a space

I'm using a MacBook with OS X installed. I'm on Terminal trying to go to a directory. So I'm in Home and I use the command ls and there is a VirtualBox VMs directory. But when I try to do cd ...
3
votes
1answer
58 views

What kinds of commands can run with exec?

What kinds of commands can run with exec? For example, executable files, builtin commands, shell script, compound commands (e.g. looping, conditional branching), pipeline, command list, commands ...
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0answers
20 views

netcat output does not write to array if launched from cron

I am able to run this script as a user or root with bash or sh. Doing so gives me the output that I expect (arrayFWS is written to file, then emailed). However, when I run it with crontab with user or ...
0
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1answer
41 views

“export VAR=thing && someCommand” reports “export: `&&': not a valid identifier”

I'm trying to set an environment variable and execute a command in a single line, like this: export PUB_CACHE=/app/src/.pub-cache && dart-sdk/bin/dart server.dart (Don't ask why... it's ...
1
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2answers
46 views

Shell eating `?` characters

This is such a simple question that I'm sure it's been asked somewhere, but I can't find it. My shell, which I have not intentionally set up to do so, seems to eat any words involving question marks: ...
5
votes
2answers
278 views

Sed with inplace editing changes group ownership of file

I have shell (php) script that gets in touch with target file this way: inspects whether file and directory are writable with php 's is_writable() (I don't think that this is problem) does in-place ...
3
votes
5answers
106 views

Bash while loop read from colon-delimited list of paths using IFS

I am trying to write a bash function that behaves similarly to the where builtin in tcsh. In tcsh, where lists all the builtins, aliases, and the absolute paths to executables on the PATH with a given ...
1
vote
1answer
27 views

bash set -o errexit problem or the way of incrementing variable?

I have a shell script incrementing a variable like in the example below with set -e: $ var=0; echo $? 0 $ ((var++)); echo $? 1 $ ((var++)); echo $? 0 $ ((var++)); echo $? 0 $ echo $var; echo $? 3 0 $ ...