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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2answers
41 views

expand wildcards “inside a command” instead of in the shell

(This is a simplest working example of something in a much messier context.) I have a directory d with files 1.txt 2.txt 3.txt 4.wav. My current directory is somewhere else. ls d reports 1.txt 2.txt ...
4
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1answer
70 views

How can I use the output of a command without using the mouse?

Imagine you issued a find command and now you want to use one line of the resulting output as an argument. $ find .. fileA fileB $ vi <CURSOR> # now do what to achive: $ vi fileB ...
2
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2answers
44 views

How do I run multiple commands together in the background?

I know I can run a program in the background using &. command & However, I want to run multiple commands, and cd into a different directory while they are running. The multiple commands ...
1
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1answer
1k views

Cannot add startup service to openWRT from init.d

I have openWrt installed on a TP-Link TL-WA901N/ND v3. I don't have luci package installed because I don't have enough space, so I can only do thing via cli. What I'm trying to achieve is to create a ...
18
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3answers
3k views

How do you output a list of all man pages in a particular section?

A man page for fork, for example, is in the System Calls section that has number 2: man 2 fork How do you see what else is section 2 without resorting to Google?
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3answers
32 views

Issue with the shell script after storing the directory in a variable

FTP is connecting to the server but i am getting an error - Enter if the env is dev or test or prod: test Please enter the id no : xxxxxxx Connected to xxxx 220 (vsFTPd 2.2.2) 331 Please specify the ...
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0answers
26 views

Regarding shell script [on hold]

I have 3 servers, one is the app server and the other two are database servers. Following are the IP addresses of my servers: App server: 192.168.1.1 DB-server-1: 192.168.1.2 DB-server-2: ...
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5answers
1k views

How to run my C program from anywhere within the System (Ubuntu 10.10)?

Friends, I want to add my C program's path to the environment variable PATH. My C program called "md5". So that I can execute it from anywhere (i.e any directory). My md5 program is located at ...
2
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5answers
375 views

How to find what device a file is on (and use that in a script)?

I want to find out what device my file is on so that I can use it in a script. I can get this far: $ df . Filesystem 512-blocks Used Available Capacity Mounted on /dev/disk0s2 498438976 ...
4
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2answers
329 views

SH: How to make vars from one script available in the main script?

I have two scripts that need to run and both require the same variables set the same way. As a result I figured I'd break the setting of the variables out into a separate script. However, I can't seem ...
1
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1answer
54 views

Safe way to install .sh script in /usr/local/bin?

I want to include correctly the following script in Ubuntu 16.04. Code #!/bin/sh # http://tex.stackexchange.com/a/20886/13173 # $Id: pdf2eps,v 0.01 2005/10/28 00:55:46 Herbert Voss Exp $ # Convert ...
0
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1answer
36 views

Script too slow ? Any particular reason?

I have a script which does hexdump along with pipeline commands and finally I am redirecting it to a file. Now I am logging data from the serial port of my Raspberry Pi. I also call a python ...
79
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2answers
3k views

Security implications of forgetting to quote a variable in bash/POSIX shells

If you've been following unix.stackexchange.com for a while, you should hopefully know by now that leaving a variable unquoted in list context (as in echo $var) in Bourne/POSIX shells (zsh being the ...
1
vote
1answer
15 views

How do I interpolate a text file of 3D coordinates (X,Y,Z) onto a regular grid?

I have a 3D surface in a text file which I need to plot on a regular X/Y grid. However, the values for X and Y are not regularly spaced and are not necessarily in ascending order. I need to regularly ...
18
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1answer
1k views

Why is /etc/shadow shortening the password that I've set with the command: useradd -p?

[root@P-dude dude]# useradd -p $6$Ic2PVlwi$2nf.IRWTMy0FHrPza6mh5wjomwbYtIIxnzxPZL7yg8SsvOdbjEpoI0G8uy7AqduYKQOn2R/rnnaalRmfPMy.a0 bwong20 [root@P-dude dude]# cat /etc/shadow | grep bwong20 ...
0
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0answers
37 views

Matching number using grep [on hold]

I have this text: yuiopao:##yuiopao:14975:Alex Vart student:/home/stud/yuiopao:/bin/bash polkovar:##polkovar:5004:John Adi student:/home/stud/polkovar:/bin/bash gfgfdgd:##gfgfdgd:11000:Alan ...
1
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1answer
41 views

Printing the file with number of hardlinks

I can print the number of hardlinks to files in directory by using find . type f -printf "%f %n\n" but this will also print the hardlink not only original files: Example: file1 is an original ...
13
votes
7answers
23k views

How to restart the Python script automatically if it is killed or dies

I am running my Python script in the background in my Ubuntu machine (12.04) like this - nohup python testing.py > test.out & Now, it might be possible that at some stage my above Python ...
0
votes
2answers
508 views

Unix Shell script to delete all traces of itself after execution through crontab

My Question has 2 parts. Help with both parts is greatly appreciated. GIVEN INFO: - Lets assume there are 2 Folders, Folder A and Folder B. - Folder A contains many files. - Folder B contains the ...
17
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9answers
13k views

How can I print lines from file backwards (without using “tac”)?

I want to print lines from a file backwards without using tac command. Is there any other solution to do such thing with bash?
4
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2answers
263 views

Float operations with bc not precise?

When I'm performing float operations in shell using bc, the result is not the same if I use a regular calculator. Am I doing something wrong? For example, I need to find a volume of a sphere. User ...
1
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1answer
48 views

Globbing error due to whitespace

My directory variable POSTMAP="/work/Documents/Projects/untitled\ folder/untitled\ folder/*/*_tsta.bam" My for statement: for file0 in ${POSTMAP}; do ... It seems that the whitespace in ...
3
votes
3answers
459 views

Is there a Unix equivalent of the Windows environment variable PATHEXT

I am wondering if there is a Unix equivalent for the Windows environment variable PATHEXT. For those with no Windows background: Adding a file suffix to PATHEXT allows me to execute a script without ...
0
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2answers
43 views

return first instance of characters from a list

Lets say I have the output of this command saved to a file. cat /dev/urandom | tr -dc '[:graph:]' | fold -w 1000 | perl -pe 's/(.)(?=.*?\1)//g' | head -n 50 I would like to compare only the first n ...
4
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2answers
53 views

Millisecond time in a shell script

How can someone print the entire time ie, for example 12:07:59:393(HH:MM:SS:milliseconds) in milliseconds. I found a lot of posts saying how to print Milliseconds along witht HHMMSS but I want to ...
4
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2answers
3k views

Testing a string containing only spaces (tabs, or “ ”)? [duplicate]

My code below doesn't work: stringZ=" " if [[ "$stringZ" == ^[[:blank:]][[:blank:]]*$ ]];then echo string is blank else echo string is not blank fi Result: string is not blank # wrong ...
7
votes
4answers
2k views

How to stop a bunch of processes on unix fast?

How to stop a bunch of processes on unix fast. I can use ps/top, kill. If the number of processes is very large, I use shell script. Are there other ways, only one or two unix commands can do it ...
1
vote
1answer
29 views

Shell is not listed in /etc/shells, when it is

I must be missing something simple here, because I am trying to make a user's default shell "lshell" for limited access. I try to set the shell with the command chsh -s /usr/bin/lshell userbut it ...
0
votes
2answers
54 views

Using regular expression to extract content of file

I have a link and I would like to return only content between www. and .com e.g www.blablabla.com would return only blablabla How could I do that? When I use grep '\.[a-zA-Z0-9\.-]*\.' it gives me ...
1
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1answer
16 views

zsh fails at path completition when command is vim

When I try to autocomplete files (with vim as argument 0): vim ~/.conf <TAB> It shows: _arguments:450: _vim_files: function definition file not found _arguments:450: _vim_files: function ...
1
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1answer
105 views

Evaluation of find ( -exec )

I'm searching for all files that contain one of a set of strings. If they do, I change their access rights. find . -type f -exec grep -q '#!/bin/bash\|#!/usr/bin/grep\|#!/usr/bin/awk' {} \; -exec ...
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0answers
33 views

How can we test POSIX compliance? [on hold]

If I want to test "POSIX compliance", can you help me script a test? I'm writing my own shell and I've scripted a test that succeeds, but my test cases are random and I don't know much about the ...
16
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5answers
21k views

How to see how many context switches a process makes?

I want to see if my process makes a lot of context switches. I also want to see how manpulating task groups affects the number of context switches.
86
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3answers
51k views

Why does my shell script choke on whitespace or other special characters?

Or, an introductory guide to robust filename handling and other string passing in shell scripts. I wrote a shell script which works well most of the time. But it chokes on some inputs (e.g. on some ...
33
votes
5answers
32k views

How can I install the `ll` command on Mac OS X?

I'm using Mac OS X. When I SSH into servers I find the ll command useful, but it's not available on my local machine. How can I install it?
4
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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 ...
2
votes
1answer
41 views

Play subtitles automatically with mpv

Subtitle files come in a variety of formats, from .srt to .sub to .ass and so on and so forth. Is there a way to tell mpv to search for subtitle files alongwith the media files and if it does to start ...
0
votes
1answer
19 views

Filtering time using last command on Solaris

I'm connected on server using Solaris and need to filter only people who were connected there until 28.4 00:00. How do I do that on Solaris? In bash I have -t option which does what I want.
0
votes
2answers
36 views

Why cant I overwrite a file with processed value?

This question prompted a thought I was not sure I understood well. I know that it is not possible or correct to use pipelines like cat myfile | grep -v mypattern > myfile due to how file handles ...
68
votes
7answers
68k views

How do you move all files (including hidden) from one directory to another?

How do I move all files in a directory (including the hidden ones) to another directory? For example, if I have a folder "Foo" with the files ".hidden" and "notHidden" inside, how do I move both ...
7
votes
2answers
1k views

Are there problems with hyphens in functions, aliases, and executables?

In my testing (in Bash and Z Shell), I saw no problems with defining functions or aliases or executable shell scripts which have hyphens in the name, but I'm not confident that this will be okay in ...
1
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1answer
24 views

Does gnome-terminal modify PATH when invoking shell

I guess gnome-terminal might have modified PATH environ variable when invoking shell. Specifically, $HOME/.local/bin:$HOME/bin will always be appended to PATH. I did the following experiment to ...
4
votes
1answer
824 views

KSH styling text based menu using STDERR

Is it possible to format the STDERR in order to have a better looking menu using the select command? I have a simple select select oChoice in $(<tempMenu.menu) ; do case "$oChoice" in ...
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0answers
27 views

Insert the environment path to script file to read [on hold]

I have a text file which has user input i.e LD_LIBRARY_PATH. I want to add the that library path environment text into the script file (/etc/init.d/scriptfilename). Will it be possible?
0
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2answers
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 ...
1
vote
3answers
314 views

the difference between '..' and “..” when I use ssh usr@ip 'pscp …'

My Server machine run Window,and it installed Cygwin. My Client machine run linux. In Clinent machine.I do this: [sikaiwei@login-1-2 v1.4]$ bash test.sh CHUN~19900405 ...
5
votes
2answers
30 views

What exactly happens if input and output file is the same?

Let's say that I execute following command: tr a-z A-Z < file > file There are two redirections: < file and > file. Both are processed before tr command and as far as I know, if there ...
2
votes
3answers
2k views

Update process name in shell, is it possible?

In C/C++ it is in general possible to do strcpy(argv[0], "new process name"). It's a hack used in malicous software to hide real process name. Is such operation possible via shell? What I want to do ...
19
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3answers
20k views

How can I remove an element from an array completely?

unset array[0] removes the element but still if I do echo ${array[0]} I get a null value moreover there are other ways of doing this but if an element of an array contains spaces like below ...
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votes
6answers
2k views

Serialize shell variable in bash or zsh

Is there any way to serialize a shell variable? Suppose I have a variable $VAR, and I want to be able to save it to a file or whatever, and then read it back later to get the same value back? Is ...