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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4
votes
2answers
52 views

Is there a way to have a function in my bash script auto run on any command error?

I'm writing a shell script that needs to do a bunch of commands and every command depends on every previous command. If any command fails the entire script should fail and I call an exit function. I ...
2
votes
1answer
82 views

clear out all variables without closing terminal

I want to know how to clear all variables which I defined in command prompt without closing terminal ? for example, if I set a variable in command prompt as: $ a=1 now I want to delete the ...
0
votes
1answer
40 views

How to monitor bunch of machines for CPU usage from another machine?

I have couple of machines as shown below which are running Ubuntu 12.04 and I need to find out the process name along with its pid whose CPU usage is greater than 70%. Below are the machines as an ...
0
votes
2answers
61 views

Run two scripts at the same time

I want to run two scripts at the same time. How exactly do I do this? If I have a variable called foo in script1 and change its value to 5, and if I'm using a variable with the same name in script2 ...
2
votes
1answer
37 views

comparing 2 lists with additional data to be printed

I have a file lets say file1.txt ENSG00000223116 AL157931.1 ENSG00000233440 HMGA1P6 ENSG00000207157 RNY3P4 ENSG00000229483 LINC00362 ENSG00000252952 RNU6-58P I have another file say ...
4
votes
2answers
249 views

How to quote arguments with xargs

Suppose that I want to delete all files in a folder that are greater than 1 MB. $ find . -size +1M | xargs -0 rm This will not delete files that have space in their names. So I want it to quote all ...
2
votes
1answer
39 views

How to suspend a process for a certain period of time?

I have several running processes which is started by a shell, but I don't want them to run during 08:00am - 20:00pm for each day because they are really bandwidth-consuming, so , I have to suspend ...
-1
votes
2answers
78 views

Check if a file is a text file in bash

I am trying to make a check to see if the file being attached to the email is a text file, and if it is not it returns an error. However during testing, I provide a valid text.txt and it returns the ...
0
votes
1answer
48 views

Script thinks input is a command?

I'm just getting started on a script that does basic shell commands, but the second function, which is supposed to take a valid year and month and plug them into cal, is returning with this error: ...
1
vote
5answers
108 views

How to get the unique count of a particular part of a string

I have a set of data in a file. psf7433-nlhrms unit7433-nobody unit7333-opera bpx7333-operations app7333-osm unit7330-partners psf7331-pdesmond unit7333-projm mnp7330-redirect unit7333-retailbanking ...
2
votes
3answers
77 views

How can I print only variables defined inside my shell script?

Lets supose some bash shell script like: #!/bin/bash a=3 b=7 set -o posix set In this case, the execution of the set variable or some other of the commands to print environment variables ...
9
votes
1answer
252 views

Security Implications of using unsanitized data in Shell Arithmetic evaluation

In a comment to a recent question, Stéphane Chazelas mentions that there are security implications to double parentheses arithmetic such as: x=$((1-$x)) on most shells. My Google skills seem to be ...
1
vote
2answers
46 views

untar shell script

i have a directory in which there are multiple tar files like tweets10_1.tar tweets10_2.tar tweets10_8.tar now i want to untar these files and keep them in a directory structure like 10_1 10_2 ...
3
votes
0answers
63 views

What default shell to use for an SSH user limited to a single command

When limiting a user to a single command via ssh, what default shell should be used for the user? This is a follow up to how can shellshock be exploited over SSH? I have a machine that is running an ...
1
vote
2answers
53 views

Extracting list of patterns which are output of another command

I can extract list of patterns using following command, fgrep -A 1 -f patternlist.txt filename.fasta but, is there a way I can extract without creating another file (patternlist.txt in this case) ...
0
votes
1answer
34 views

Why PPID is different when opening from terminal and when opening by doubleclicking

I am using Linux. When i opened gedit program in gnome-terminal by gedit command it has opened the graphical gedit text editor. then the gedit has PPID bash ...
8
votes
5answers
587 views

Convert file contents to lower case

I have temp file with some lower-case and upper-case contents. Input Contents of my temp file: hi Jigar GANDHI jiga I want to convert all upper to lower. Command I tried the following command: ...
1
vote
3answers
126 views

How to print new lines at the end of functions?

If I type echo hello, my terminal looks like this: My-Computer:~ user$ echo hello hello My-Computer:~ user$ But if I have a function like this stringen () { cat /dev/urandom | env LC_CTYPE=C tr ...
2
votes
3answers
47 views

SSH command with file redirect not working

I want the following command's result to redirect into a file on the remote server, as I want only unique lines in my authorized_keys file: ssh root@10.100.10.26 awk '!seen[$0]++' ...
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 ...
1
vote
1answer
40 views

bind -x leaves terminal in a state resembling ^V

I define a shell keybinding in my ~/.bashrc like so: bind -x '"\e\C-w":"/usr/bin/reset"' This does make Ctrl-Alt-w launch the reset executable. However, it leaves the terminal in a state that ...
42
votes
1answer
967 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 ...
0
votes
2answers
42 views

append time to log filenames

I want to make log_files named as log_Jan_01_hh:mm:ss, so the variable time-stamp is defined as date +"%b_%d_%T". Now if I set the value to a variable: setenv now `date +"%b_%d_%T"` Then $now ...
2
votes
1answer
46 views

Find Command: File Path vs -name Argument

I'm currently building a script to handle some files in a directory. In the first example, I use the find command and pass a directory in as the argument. In the second I instead use the -name switch ...
0
votes
4answers
60 views

Print last character in the given path

I am trying to concat "comnp.dat_CY*" files into one file. File name, source path and destination path are the parameters. I am trying to find the last character in the path to check if it is "/" or ...
2
votes
2answers
46 views

find and delete gives false status

I tried to execute delete as per many previous discussions occurred find & delete however my attempts lead to different experience. find . -type d -name "koko" -exec rm -rf {} \; deletes the ...
2
votes
0answers
58 views

Read output in `screen` from outside

Suppose I opened up a screen to run some program that outouts some result. Once the program finishes, is there a way to get the result in the screen from outside. For example: I opened up a screen ...
0
votes
1answer
58 views

Shell script runs differently when schedulled with cron

I have a strange problem with my backup script. To begin with, this is the backup script: ########################################################### # CODE BEGINS HERE ...
2
votes
2answers
61 views

Event not found in sed call in csh script

I tried the code as given on delete text between curly brackets however I am facing this different error regarding event in sed. file contains: This is { {the multiline text} file } that wants { ...
2
votes
2answers
40 views

How to specify a different “top level” name for tar?

I would like to tar root (/) and let it appear as /abc in the tar archive. Is there a tar flag for specifying a custom top-level name?
-3
votes
1answer
32 views

How can I apply floating point discounts and taxes in a shell script?

I want to input a number and then add taxes and subtract discounts. I am trying: #!/bin/sh printf "Please enter purchase amount: " read purchase_amount if test $purchase_amount -lt 1000 then ...
0
votes
1answer
425 views

Run bash script on startup in Linux Mint and open mate-terminal automatically

I'm new to Linux, so not sure how to do what I want. I have my_script.sh (executable, of course) like this: #!/usr/bin/env bash mate-terminal -e "bash -c 'cd ...
0
votes
0answers
33 views

Extracting trace information using gawk

I am new to awk programming and am using gawk to extract trace information from a mrt file in order to use it further for analysis. I have successfully been able to extract trace information from a ...
1
vote
1answer
46 views

How do I add something to the end of “}” if a pattern is matched?

If I have something that looks like this: hello {sdsdsdsds} pattern {askjdasjkdjasd} hello {siadsd} pattern {iuewer} So if pattern if matched before {*}, I need to add a ;. Output: hello ...
1
vote
1answer
45 views

login/non-login and interactive/non-interactive shells [duplicate]

Are the concepts of login/non-login shells the same as the concepts of non-interactive/interactive shells (respectively)? Or are the concepts orthogonal yielding four different combinations? I am ...
2
votes
4answers
83 views

How do I use newlines inside () with sed?

When I want to replace, say Dot with Dot ##empty line## I do this: sed 's/Dot/Dot\ /g' Yes, a literal new line, this is the way it works on BSD sed. But, I can't do the same when the sed is ...
2
votes
2answers
67 views

How to search empty alternation with tcsh

I want to search some empty alternation with ls but nothing is working. I have a list of files: foo.txt foouubar.txt fooubbar.txt fooubar_1.txt foounix.txt I want to have only foo.txt and ...
2
votes
3answers
77 views

Bash: issuing trap twice

I have a very simple question. I can't believe the Bash manpage doesn't explain this already, but anyway... If I issue the trap builtin twice [for the same signal], what happens? Is the second ...
2
votes
1answer
51 views

Execute command that was displayed on the screen as a message

A message is displayed many times on the screen after entering certain command. I need to retype the entire suggested command or copy and paste it. Is there a shortcut to do the same using the ...
0
votes
2answers
54 views

Why doesn't this pipe command work at this special bash script?

That script test.sh doesn't work after used pipe command. The result shows nothing. Why? #!/bin/bash fun=$( echo $1 ) echo "$fun" commands are as follows, $ echo 1 | ./test.sh
3
votes
1answer
58 views

Problem with getting interactive input in while read loop

I was doing something like the following minimal example: #! /bin/sh # $1 = file containing list of files to sync # $2 = source dir ; $3 = target dir cat "$1" | while read f do cp -i "$2"/"$f" ...
1
vote
2answers
145 views

Can I hook into the cd command?

I'm trying to set something up on a server I run, when ever I cd into a public_html folder 95% of the time there's a few commands I will always run to check certain things. Is there anyway I can hook ...
7
votes
4answers
563 views

List the number of lines in files

How can I list the number of lines in the files in /group/book/four/word, sorted by the number of lines they contain? "ls -l" command lists them down but does not sort them
2
votes
2answers
258 views

How to create an alias for a sequence of commands? [duplicate]

I know it for one command but how to work with a sequence?
1
vote
2answers
53 views

how to extract path from file location using shell [duplicate]

how to extract path location from below given string. /opt/oracle/app/oracle/product/12.1.0/bin/tnslsnr expected output. /opt/oracle/app/oracle/product/12.1.0/bin (or) ...
1
vote
5answers
155 views

find the max value of column 1 and print respective record from column 2 from file

How to find the max value from the column 1 and echo the respective path location from a file which contains n number of records. $ cat version.log 112030 /opt/oracle/app/oracle/product/11.2.0 ...
6
votes
4answers
325 views

what's the difference between using 'single quotes' or not in find command

find ~/ -name *test.txt find ~/ -name '*test.txt' Can anyone help me to construct an example where the first form fails but the second still works. And tell me the difference between them.Thanks!
2
votes
3answers
87 views

How to parse env variable in a quoted string?

I'm having a hard time getting the value of an environment variable ($GHREPO) in a quoted string. Here is the command I'm running. I'm trying to make a directory with the value of ...
2
votes
2answers
116 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 ...
2
votes
1answer
86 views

find and sed (find and replace) causes illegal byte sequence on Mac OS X

I am attempting to perform a find and replace of underscores to dots in a directory for certain filetypes only (.mkv, .mp4, .avi). This is the code that I am using (I'm on Mac OS X 10.9): find . \( ...