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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5
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3answers
3k views

How to prevent command injection through command options?

I have an wrapper application where I need to let the user specify custom options to pass to a simulator. However, I want to make sure the user doesn't inject other commands through the user options. ...
2
votes
1answer
1k views

GUI apps don't inherit PATH from parent console apps [closed]

In Gnome, don't GUI applications inherit the PATH of the shell process that launches them? Apparently, GUI applications see only the PATH specified in ~/.profile. No issues with console applications, ...
4
votes
1answer
1k views

How can I use tee and logger -t “some tag:”?

I've seen in another post which shows how to use tee and logger as shown below. tee >(logger) <<< "System Load is OK : $Current_loadadv" >(logger) is bash syntax to create a file ...
0
votes
1answer
748 views

Tab autocomplete for files with spaces in it [closed]

How do I tab autocomplete for files with spaces in it? Thanks.
0
votes
2answers
10k views

Read the output of a command into a variable [duplicate]

I am making a bash script but I'm totally new and got lost. I've made this code cat * | grep "|*parameter1*|" | grep "|*parameter2*|" | cut -f 8,11,12,15,21,23,34 -d "|" | wc -l which works just ...
2
votes
2answers
3k views

How to download the latest file in a folder using a scp?

I'd like to run an scp transfer to download the latest (newest) file in a certain directory to my local directory. Something like this: source: root@rimmer.sk:/home/rimmer/backups/ destination: ...
1
vote
1answer
618 views

Can't access command history in my shell (sh)

I'm not sure if readline is what really missing but the problem is shell (instead of bash) and when I click the up and down arrow I get the following instead of command history: $ ...
2
votes
2answers
121 views

how to count number of differences in large streams quickly?

I want to count the number of differences (different bytes) in two large streams (devices/files). E.g. two hard disks, or one hard disk and /dev/zero. The program(s) involved must be fast, as fast ...
10
votes
2answers
393 views

What is the difference between “*.pl” and *.pl in grep? Why does quoting change the result?

What is the difference between: grep "string" . -r --include *.pl and grep "string" . -r --include "*.pl" The latter includes files in subdirectoried while the former not. Why?
4
votes
1answer
198 views

How to concat file and a line on-fly?

I would like to send to the stdout entire file + extra line. How to do this nicely? So far I did: for LINE in $(cat $INPUT_FILE) do echo $LINE done echo $EXTRA_LINE How to do this bash way (for ...
1
vote
2answers
2k views

How can I make “bind” command to work in sh shell

How can I make the next script to run when I'm using sh shell: #!/bin/bash bind '^[[3'=prefix-2 bind '^[[3~'=delete-char-forward bind '^[[1'=prefix-2 bind '^[[1~'=beginning-of-line bind ...
3
votes
2answers
925 views

Bad substitution inside xargs subshell?

I'm using this command to process PNG files: find . -iname "*png" -print0 | xargs -r0 --max-procs=4 -n1 sh -c 'pngnq -s1 $1 && advpng -z -4 -q ${$1%.*}-nq8.png' - It seems to actually work ...
1
vote
1answer
227 views

Delete key doesn't work properly in PHP interactive shell

In the interactive shell oh PHP Delete key is not working and produce ~ instead. Anyone know how to get this key to work? I am using Ubuntu 13.04 if this does matter.
0
votes
3answers
598 views

Renaming all files in a directory while keeping the same initial part of the name [duplicate]

I have a directory full of files. I want to rename all the files that match *.py to -backup.py. How do I do that. I know I can use for i in *.py, but from there I'm not sure how to keep the ...
4
votes
2answers
774 views

how do I reference a variable in fish shell with a default fallback

What is the fish shell equivalent to the following bash: echo ${TEST:-1} In bash this would print the value of TEST if there was one, or 1 if there was not.
63
votes
5answers
43k views

How to go to the previous working directory in terminal?

In terminal, how can I define a key to go to the previous directory which I was in when changing directory with the cd command? For example, I'm in /opt/soft/bin and I cd into /etc/squid3 and I want ...
2
votes
2answers
723 views

Use a different shell by default in each terminal emulator

I would like to change the default shell in each terminal emulator separately. To clarify, I want Xterm to use TCSH, pterm to use pysh, gnome-terminal to use BASH, etc. Is this possible? If so, how ...
2
votes
1answer
265 views

Change the default shell to Python

If I changed my default shell from BASH to Python3 or IPython, would my Linux system have issues or produce errors?
4
votes
3answers
4k views

How to stop redirection in bash

I use : exec >script.log 2>&1 in my script to redirect all output to a file. At the end of the script I would like to print a message to the screen. How do I stop the redirection?
3
votes
3answers
14k views

change shell in Solaris/SunOS for your user only wihtout access to /etc/passwd

How do I set the shell in Solaris/SunOS for my user only, without access to /etc/passwd or any other su stuff? It should thereafter work both for interactive ssh (1) and ssh when you send commands ...
0
votes
0answers
19 views

C Shell Array Declaration Syntax, () vs. {} [duplicate]

In my C-shell script (tcsh specifically) I have been trying to declare an array with six values: x, nx, y, ny, z, nz. After some trial and error I discovered three different ways of declaring the ...
4
votes
5answers
255 views

Standard unix util to split “foo.bar.baz” into “foo.bar” + “.baz”?

I want to split a string $basename, containing the output in two parts, $stem and $ext, such that: the string "${stem}${ext}" is identical to the original string $basename; either $stem or $ext may ...
3
votes
2answers
6k views

How do I run a command on multiple files

This is pretty basic, I have a folder with several subfolders of JS files and i want to run Google's Clojure compiler on all of the files in those folders. The command to process a single file is as ...
21
votes
4answers
11k views

Why does `cd` command not work via SSH?

I was trying to backup some files via SSH but instead of tar'ing the ones I wanted I got my home folder. I did some further testing and it boils down to this: ssh root@server /bin/sh -c "cd /boot ...
1
vote
4answers
625 views

Command substitution grepping ls output causes error

I'm trying to make a tar.tgz file using command substitution There are backups of 17 Aug 2012 -rw-r----- 1 ossec 502 804M Aug 17 2012 BKPMDISINT_i6nir20j.F_bkp -rw-r----- 1 ossec 502 2.7G Aug 17 ...
17
votes
3answers
40k views

how to output text to both screen and file inside a shell script?

Currently I have a shell script which logs messages to a log file like this: log_file="/some/dir/log_file.log" echo "some text" >> $log_file do_some_command echo "more text" >> $log_file ...
16
votes
1answer
18k views

Redirect both stderr and stdout to /dev/null with /bin/sh

Tried all sorts of ways to redirect both stdout and stderr to /dev/null without any success. I have almost my entire life run bash which i've never had this issue with but for once in BSD i'm stuck ...
4
votes
1answer
2k views

Use the terminal's autocomplete path feature for input to a shell script

I want to make a script that: (1) Gets a path giving the user the ability to use tab to autocomplete, then (2) gets a filename from the user, and then (3) creates a file at that path with extension ...
5
votes
3answers
6k views

How do I run a shell command from .tmux.conf

How do I run a shell command from .tmux.conf, or otherwise automatically when tmux launches, without having to hit any other command? How can I create an alias, a function, or a script which boils ...
1
vote
1answer
940 views

How to filter an array of strings in ksh

Please advise what's wrong in my ksh code. I want to remove the IP's as defined in "bb" array from "aa" array so the IP's 255.0.0.0 and 255.255.255.0 will be removed from the list in aa array. When ...
19
votes
3answers
1k views

Show PATH in a human-readable way

I want to show my PATH environment variable in a more human-readable way. $ echo $PATH ...
5
votes
3answers
105 views

How can I remove a file called “--help” with bash command line? [duplicate]

I've somehow managed to create a file with the name "--help". If I try to remove the file using "rm" funny stuff happens. Please help here's a printout of the dir listing: [pavel@localhost test]$ ls ...
1
vote
1answer
536 views

I quite like mercurial .hgignore-style globbing. Is there a Linux shell that supports it?

I quite like mercurial .hgignore-style pattern globbing. Globs are rooted at the current directory; a glob such as *.c will only match files in the current directory ending with .c. The ...
3
votes
2answers
258 views

Cron job for every minute executing out of order?

I'm setting up some shell scripting to be executed every five minutes, then every minute on our client's system, to poll a log and pull some timing information to be stored and accessed by another ...
10
votes
4answers
28k views

how to count total number of words in a file?

I am looking for a command to count number of all words in a file. For instance if a file is like this, today is a good day then it should print 5, since there are 5 words there.
4
votes
3answers
1k views

Reading a binary file as an array of bytes or 16 or 32 bits using shell script

I am working on ARM-based modem Linux host machine and I need to read a bin file as an 8-,16- or 32- bits array. I basically need to encrypt the file in question and was thinking of just XOR-ing the ...
2
votes
3answers
1k views

how does built in commands of a shell implemented in Linux? as a function or thread of shell process?

I know that external commands are run in the shell by creating a separate process. But what exactly happens when a built in command is run in a shell. Are they executed as a function or if the shell ...
0
votes
3answers
114 views

Is there a way to switch to “su -” after switching users through “su”?

Maybe the title wasn't worded quite clear. But basically what I want to be able to do is to switch to having used "su -" instead of the traditional hyphenless "su" after already using "su" to switch ...
3
votes
3answers
4k views

Why do 'ssh host echo $PATH' and printing the $PATH after ssh'ing into the machine give different results?

On a particular host, when I ssh into the machine and enter echo $PATH I get /home/wxy/bin64:/home/wxy/bin:/usr/kerberos/bin:/usr/local/sbin:/usr/sbin:/sbin:/usr/local/bin:/bin:/usr/bin and if I ...
4
votes
2answers
37k views

“not a valid identifier” when I do “export $PATH”

When I run export $PATH in bash, I get the error not a valid identifier. Why?
6
votes
2answers
4k views

How to trigger error using Trap command

I am using Ubuntu 12.04.2. I am trying to use "trap" command to capture abnormal or error in my shell script but I am also trying to manually trigger "Error" exit. I have tried exit 1, but it won't ...
0
votes
0answers
556 views

Easy way to push data into MongoDB from Bash shell script?

I know you can create a Javascript file that the MongoDB shell will execute upon startup. But I'm hoping for something more "lightweight" than that. I am using a Linux program that has a scripting ...
6
votes
3answers
963 views

cd to directory of a symbolically linked file

Before I write a script, anyone know an easy way to do the following: $ pwd /foo/bar $ ls -l lrwxr-xr-x 1 username admin 48 Apr 17 2012 foo.sh -> /bar/foo.sh $ cd /bar $ ls foo.sh i.e., in ...
10
votes
2answers
6k views

Executing piped commands in parallel

Consider the following scenario. I have two programs A and B. Program A outputs to stdout lines of strings while program B process lines from stdin. The way to use these two programs is of course ...
7
votes
3answers
27k views

Terminating a bash shell script running in the background

I often use bash shell scripts to run simple commands for many different files. For example, suppose that I have the following bash shell script, called script.sh, that runs the program/command foo ...
-1
votes
1answer
452 views

SED command and filenames with space

I was hacked, for my php files was infected. Example: http://www.nwww.ma.mk/oscommerce/configweb/apexfash-wp-blog.txt Bad Code: <?php ...
0
votes
2answers
249 views

Why are there empty lines in the output of my command?: find ~/x/y/ | shuf > ~/Desktop/z.txt

As it turns out the reason for this problem was one filename with several newlines. (No idea how that happened.) find ~/x/y/ | shuf > ~/Desktop/z.txt This command works pretty much as expected ...
4
votes
2answers
944 views

Convert MAC address to Link-local address with bash

How can I convert a Mac address into an ipv6 Link-Local address? you have to add fe80:: at the start and insert ff:fe in the middle furthermore all leading zeros must be stripped
5
votes
2answers
10k views

how to loop through arguments in a bash script

I would like to write a bash script with unknown amount of arguments. How can I walk through these arguments and do something with them? A wrong attempt would look like this: #!/bin/bash for i in ...
4
votes
4answers
483 views

How to deal with spaces in a variable

I'm working on some scripting: for x in `find ./ -name *.pdf` do echo pathname $x done My filenames are Test1 ( Volume II), Test2 ( Volume II). I'm getting a return of pathname Test1 pathname ( ...