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
77 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
46 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
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5answers
107 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
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3answers
76 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
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1answer
251 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
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2answers
45 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
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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
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2answers
51 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
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1answer
33 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
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5answers
571 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
125 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
46 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
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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
39 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
965 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
44 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
59 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
45 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
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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
55 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
59 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
39 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?
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votes
1answer
31 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
410 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
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0answers
32 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
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1answer
45 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
82 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
66 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
76 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
50 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
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2answers
53 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
55 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
144 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
558 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
257 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
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2answers
52 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
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5answers
151 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
324 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
83 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
114 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
84 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 . \( ...
4
votes
2answers
102 views

Using `case` to handle script arguments

Can I use the case statement to handle arguments? So, using -restart I'd like execute "-umount" and "-mount" #!/bin/bash case "$1" in -mount mount /ip/share1 /local/share1 ;; -umount umount ...
1
vote
1answer
133 views

How do I put a time stamp with: wget --output-file=[FILENAME] [URL]

So I've been trying to put a timestamp on some images I'm downloading from a webcam, but so far it's been saving the images with the names camera3_date' here's my line that I enter: wget ...
0
votes
1answer
88 views

check status process output

I wanted to understand how to create a script sh that allows me to see if an additional script functions correctly. For now this is the script that I created. if /run.sh status echo "$SERVICEXE ...
1
vote
2answers
73 views

Compare and print data from different text files to one in Shell

How can I compare and print data from different text files to one in Shell. I have captures NAS details of three different boxes using SSH, now I need to combine all the three text files to one file ...
0
votes
1answer
47 views

Trying to debug /etc/init.d/named, no output, replace > /dev/null with /var/log/named.log?

I'm trying to debug named, when I try: [root@test master]# service named start Starting named: [FAILED] it fails silently, so I tried: sed -i ...
33
votes
3answers
2k views

Why is using a shell loop to process text considered bad practice?

Is using a while loop to process text generally considered bad practice in POSIX shells? As Stéphane Chazelas pointed out, some of the reasons for not using shell loop are conceptual, reliability, ...
1
vote
1answer
162 views

How to keep running a process in Android when disconnecting adb terminal? command “nohup” not found

I'm trying to analyze the reason for random reboots of my phone (see here). Therefore I wanted to record the logcat and kernel messages till the restart to see the logs even after the usb disconnects, ...