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
0answers
4 views

Linux: set command for local variables

I am trying to understand local/environment variables and export/set commands. $ set FILEM="razrax" $ echo $FILEM $ FILEN="test" $ echo $FILEN test Please explain why echo $FILEM returns empty ...
-2
votes
1answer
14 views

Delete line from files

I have 8 files in a folder. If any of these files has 2 lines I need to remove the second line from that file. If a file has more than 2 lines then then I do not need to do anything to it. Can anyone ...
2
votes
1answer
29 views

Prevent glob expansion in foo=“*”; echo $foo [duplicate]

In Bash, when I do: foo="*" echo $foo It expands * to the contents of the current folder. How do I make sure it just prints a literal *? The same, by the way, happens with a regular echo "$foo", ...
1
vote
2answers
20 views

CentOS 7 shell script interpretor

I am starting to write a shell script to be run in CentOS 7. Which interpreter should it call, and what should the shebang line look like? I tried this: #!/bin/sh But when I type cd /bin ...
2
votes
2answers
41 views

How to I prevent exec from keeping the script running?

I'm using exec like this: #!/bin/bash exec > >(tee /tmp/mylog.log) 2>&1 bash -c 'sleep 12312' & I want the output of the commands to be in a log file, and then I want to start a ...
0
votes
1answer
29 views

In-place substitution for paste command [duplicate]

When I run the following code echo '1' > file.txt echo '2' | paste file.txt - > file.txt I would expect the content of file.txt be 1 2, because the paste command as it name suggests should ...
-1
votes
1answer
27 views

Quoting a URL string containing & in sh script [on hold]

I want to put quotes "" marks around a string which has the & symbol in it. If I echo the string, the shell treats the string as two commands, ie. separated by the &. Looking for something ...
2
votes
2answers
51 views

Use alternatives or adding to PATH?

I'm a bit confused about the proper way to make a script globally available from the terminal, like a command. There are two ways, using the alternatives utility, basically making a symlink to ...
1
vote
0answers
11 views

Setting custom baud rate on console

Just for aesthetics I would like to have my text on my console be displayed at a lower speed. I've tried using things like screen with custom baud rates of /dev/tty1 but it wouldn't work, input from ...
2
votes
2answers
48 views

how to sort by the day of the week?

I have two files. file1: Dave 734.838.9800 Bob 313.123.4567 Carol 248.344.5576 Mary 313.449.1390 Ted 248.496.2204 Alice 616.556.4458 file2: Bob Tuesday Carol Monday Ted Sunday ...
0
votes
3answers
40 views

Bash: Access parameter passed to last command [duplicate]

This is a situation I often find myself in: mkdir /Some/really/long/path/to/a/directory/ cd /Some/really/long/path/to/a/directory/ I know that ideally you would cd /Some/...etc.../a/ and then mkdir ...
-3
votes
2answers
28 views

What is the exact difference between “/” and “%” in the expr command?

I want to know the difference between "/" and "%"! When I type and run the following command I get 0: expr 4 % 4 But when I run same command and replace "%" with "/" I get 1 expr 4 / 4 Thanks
4
votes
3answers
462 views

Echo command with AND operator doesn't exit

echo hai && echo bye prints hai bye while echo hai && echo $? prints hai 0 When the first echo command's return value is 0, how does the echo statement after AND operator ...
7
votes
2answers
316 views

How to store a large folder in a single file without compression

Sorry if this is a stupid question, but I want to take a 78gb folder and store it in a single file (for upload into a cloud service), as if I am compressing it in an archive, but I don't want any ...
2
votes
2answers
48 views

Create variables and assign values via loop (bash)

Is there a way to create bash variables and assign them values via a loop? Something along the lines of: #!/bin/bash c=0 for file in $( ls ); do var"$c"="$file"; let c=$c+1; done EDIT: ...
1
vote
2answers
76 views

How can I select 3 character files in Bash?

I know that a question mark is considered a special character and it has special meaning. Question mark represents a single character that can be any type. In my practice lesson we have an example : ...
0
votes
0answers
23 views

Show last x lines of a screen session?

/etc/init.d/mc {..} status) if screen -ls | grep -q "mc"; then echo -e "[\033[32mMC\033[0m] Online" {.. needed code ..} else echo -e ...
1
vote
1answer
71 views

Bash script won't work on current directory

I'm using Kali linux which is based on Debian and wrote an script to copy some files from where the script is based to a specified directory. But when I execute my script (called CopyFiles.sh), cp ...
0
votes
0answers
14 views

Create user, directory, vhost, and mysql user faster? [on hold]

I host a lot of my client websites on my dedicated Ubuntu Server (14.12). I really need a faster way to create a directory for a new client then manually creating the user, the mysql user, assign the ...
1
vote
1answer
38 views

Can't use find -print in AWK

I'm trying to put together a command to find SUID System Executables, which are not the default ones in RHEL. To do this, I'm pulling a list of the local File System (df --local -P), piping it over ...
3
votes
1answer
31 views

How to inspect the raw contents of a partition?

I'm trying to see the contents in raw bytes of a dummy partition /dev/sda3, which I've made to be 100MiB through gparted. I want to test writing and reading on that partition. Is there a tool that ...
0
votes
2answers
30 views

Change only the year on the output of the “date”-command

date for example displays Fri Apr 17 20:16:01 IST 2015 Now I want to change only the year so date should display Fri Apr 17 20:16:01 IST 2016 in this example. How to add 1 year to the output of date ...
2
votes
2answers
42 views

Local variable as a part of global one

I have a question about something similar to this question, but I need to call global variable depending on local one. Say I want to pass either test, staging, or production as a variable to a ...
3
votes
1answer
31 views

Shell glob - substitute file path arg with file's contents

In curl command, there is --data option, which substitutes the file contents when the option value is prefixed by @ symbol like, curl -X POST --data @abc.json hostaddr.com abc.json file contents ...
13
votes
3answers
482 views

When I cd through a symlink, why does pwd show the symlink instead of the real path?

I created a soft link (ln -s 1 2) to a directory which is inside the test directory and opened the soft link (cd 2) and displayed the current path using pwd. The displayed path was ~/test/2 and not ...
2
votes
1answer
20 views

Quoting: loop over ssh-accounts, call psql on remote server

This works in the human brain, but the shell misses quoting: for h in a b; do ssh $h psql -tAc "select * from mytab where mycol='x'"; done How to quote this one liner without loosing readability?
0
votes
1answer
47 views

How can I get a shell script to change directory for me? [duplicate]

here is a small test I ran, to try and move me back to root: #!/bin/bash pwd cd / pwd It returns the current working directory, and then the correct new one, but when the script finished executing, ...
2
votes
2answers
178 views

The «sh» being launched with execl() becomes a zombie

I am spent whole half a day, but still couldn't figure, why is the dash being launched with execl call just becomes a zombie. Below is a minimal test case — I'm just fork a child, make a duplicate of ...
1
vote
1answer
43 views

using `for file in` to select multiple extension names then get the basename of “file” then concatenate an extension name

I am trying to practice my unix skills, I just learned how to use for file in *.jpg; what it does is select all files with .jpg in the working directory, but I do not want to stop there and I do not ...
0
votes
1answer
39 views

how to write a shell script to run multiple programs

I want to run two programs ssh -f mike@c15-0330-02 'cd /home && nohup Rscript L_1.R> L_1_sh.txt ' AND ssh -f mike@c15-0330-03 'cd /home && nohup Rscript L_2.R> L_2_sh.txt ' I ...
0
votes
0answers
42 views

Need to have password coded in script [duplicate]

I have to login many Servers day in day out by supplying passwords manually. Now I want to know or have a script where from I can login to any server without password (I mean to say if the ...
0
votes
1answer
38 views

shell script unable to set environment variable with the grepped value

In the shell script, I want to grep a value from the log file and set as the value of one environment. In the log file, there is one line like this: SOME_PATH=/some/specific/path In my shell ...
1
vote
1answer
34 views

Cut some fields from a text file to another

I have the following command: grep -owf champs.txt t.txt and I want to cut the result of this command from the file t.txt to another file. I know that it can be achieved by a nested command but I ...
1
vote
2answers
66 views

How are long command lines ( > $COLUMNS ) automatically wrapped to a new line?

There are several points where I/O is passed through, some of which (to my knowledge) are the shell, pty, tty, termios, terminal emulator application. In most terminal emulators, long command lines ...
1
vote
2answers
78 views

check if a variable is in list

to check if a word is in a list of words or no I wrote this script: tr -s '[[:blank:]]' '\n' < t.txt | while IFS= read -r word; do if [[ "$word" =~ $(echo ^\($(paste -sd'|' ./champs.txt)\)$) ...
1
vote
1answer
43 views

Given a *nix command, how do I find where the executable is? [duplicate]

There is a command written in bash I found from documentation from people who previously worked in this project. Now I need to locate the command's source and modify it. I tried which my_command ...
0
votes
2answers
45 views

How to search recursively in a directory for different files?

I have a x.tar file in directory /a. After untaring x.tar I got the following result: cust/ cust/01/ cust/01/INFENG/ cust/01/INFENG/scr/ cust/01/INFENG/scr/test.scr cust/01/INFENG/SQL/ ...
5
votes
2answers
450 views

How can I make xargs play nice with stdin?

$ seq 1 3 1 2 3 $ seq 1 3 | xargs echo 1 2 3 $ Mentally replace seq 1 3 with any command that lists entries one-per-line on standard out. How can I get more-or-less what you'd expect, i.e. the ...
5
votes
4answers
232 views

Change the time zone of a cronjob

I have a cronjob which is executes every day at 9:00 AM of UTC-Time. I'm in GMT+1 so it executes at 10:00 AM local time. When there is the timezone change (to daylight saving time, DST), the cronjob ...
1
vote
3answers
91 views

Bash long string, no word splitting?

I want to tidy up some script with long commands, so that for example: { somecheck || somecomand "reallyreallyreallyreallyreallyreallylongstring" } &> /dev/null & becomes something like: ...
1
vote
0answers
23 views

What Does the Output of “--help” Mean? [duplicate]

When using the --help option of a terminal program, a lot of output is produced. It usually starts with Usage: and then a bunch of things and brackets and parentheses. My question is, what doe the ...
0
votes
0answers
37 views

chrome os: crosh tab completion

Tab-completion doesn't seem to work in crosh, or even in other Chrome OS apps - it kind of does what's expected, in that it tabs to the address bar, but unfortunately that's not what I want. I could ...
2
votes
3answers
73 views

bash: error handling on find -exec

I was using this little script to find malformed images: find -name '*.jpg' -exec identify -format "%f\n" {} \; 2>errors.txt It worked well enough, but now I need to modify it slightly. Instead ...
0
votes
0answers
42 views

Counting program fails in arithmetic test

having a little trouble with this rather basic script. This script works on Bash in my macbook pro, but not on my Linux Mint desktop, which also uses bash. I can't figure out what's wrong with it, ...
2
votes
1answer
45 views

Bash - Command substitution adds single quotes

I have a problem with bash behavior while evaluating grave accents. I want to run find with optional -name: find -name "*.log" works fine, but when i want to get the -name part from nested script ...
0
votes
1answer
45 views

Print file name,Modified Date and Size with Header

How do I print file size, file name and modified date with header.Till now I have come up with: find . -regex '.*\.csv' -execdir stat --printf '%n,%y,%s' {} \; How to add header and do not print ...
1
vote
1answer
55 views

Running some parts of a script as an unprivileged user with shell environment

I am creating an instance configuration script that sets up a machine. I am running the script via sudo i.e. sudo run.sh. Most of the steps require root access but some of the script's steps do no ...
1
vote
4answers
52 views

Sed substitution grouping is appending in OSX rather than the expected sub in Linux

I've got three comma separated columns. Last name, First name, social. I'm trying to capitalize all characters in the last name column using sed 's/\([^,]*\)/\U\1/' foo.file In osx this command ...
2
votes
1answer
34 views

Syntax When Combining dd and pv

I am a linux newbie; so, sorry if this is obvious to you... sudo dd if=/dev/sda bs=64k | pv --size 1.5t | dd of=/dev/sdb Does the block size for dd go on the left side of this after the input as ...
-2
votes
1answer
91 views

Sqlplus: Command not found

I have two virtual machines ubuntu, one is a server when I installed oracle 11g express, and the other is a simple client. My goal is to run an sql query remotely from the client machine. So I ...