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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1answer
372 views

error using “du” command

I am on the university machine trying to estimate the disk usage I have on my space I do du -csh ./ from the begining of my account, but an error is given that ./Yesterday/Yesterday is not a ...
8
votes
5answers
17k views

how do I add newlines between lines printed on the command line?

Mail logs are incredibly difficult to read... how could I ouput a blank line between each line printed on the command line. For example say, i'm grep-ing the log. That way multiple wrapped lines ...
4
votes
1answer
2k views

Read space as input in shell script [duplicate]

How can I give space " " as input in shell script ? Ex : echo " Enter date for grep... Ex: Oct 6 [***Double space is important for single date***] (or) Oct 12 " read mdate echo $mdate I get the ...
18
votes
4answers
9k views

Save complete GNU screen session state

Is it possible to persist the "state" of a GNU screen window (or just a standard shell) so that I can reload everything after a reboot: The number of opened shells The name of each shell The current ...
40
votes
7answers
47k views

How do I convert an epoch timestamp to a human readable format on the cli?

How do I convert an epoch timestamp to a human readable format on the cli? I think there's a way to do it with date but the syntax eludes me (other ways welcome).
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votes
3answers
321 views

Correct textual name for <<

I've just come across the << command, used like so: cat > outfile.txt <<EOF Multi-line content that will be written to outfile.txt EOF Now, I've no idea what this is called, but I'd ...
6
votes
7answers
2k views

Is it bad practice to set root's shell to something other than the default?

Once a friend of mine (who is an experienced Unix/Linux user) told me that setting root's shell to something other than sh (i.e bash or zsh) might create problems, because some script might assume ...
3
votes
5answers
3k views

how to pass the result of `find` as a list of files?

The situation is, I have an MP3 player mpg321 that accepts a list of files as argument. I keep my music in a directory named "music", in which there are a few more directories. I just want to play all ...
6
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1answer
3k views

how to view a directory's permission

What is the command with which you can directly view the permission bits of a directory?
4
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3answers
1k views

`$XAUTHORITY` appears from 'nowhere' on su+tmux

When I switched from su+bash to su+tmux+zsh I noticed that I get $XAUTHORITY variable defined as /root/.xauthXXXXXX where XXXXXX are 6 random alphanumeric characters. With previous configuration X ...
1
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1answer
93 views

how to convert ^I character

I have a text file like this: info Some info here In which when I use cat -A display this: info^I Some info here How do I edit this so I'll get something like this instead: ...
1
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2answers
325 views

Problematic build script with quotes

Hi I'm trying to create a build script that executes these commands: cd libiconv ../../src/libiconv/configure --prefix=/home/ruben/mingw64/build/gcc-libs \ ...
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0answers
327 views

bash: recall command by typing some characters of it [duplicate]

Possible Duplicate: best way to search my shell's history In MSDOS I have the option to start typing some characters of a previous command and then pressing F8 it will search the ...
2
votes
2answers
1k views

Extending history search in zsh

How to extend Ctrl+R search in zsh? It cannot find entry despite it is in history file. Edit: My .zshrc: setopt AUTO_CD setopt CORRECT_ALL setopt EXTENDED_GLOB # History SAVEHIST=10000 ...
16
votes
9answers
11k views

Tool in UNIX to subtract dates

Is there any tool in Solaris UNIX (so no GNU tool available) to subtract dates? I know that in Linux we have gawk that can subtract one date from another. But in Solaris the maximum we have is nawk ...
5
votes
2answers
1k views

dash compatibility to bash

Wikipedia says that dash executes faster than bash. My question is, if I set /bin/sh to dash, will all scripts that use /bin/sh in their shebang line that was intended for bash work under dash?
5
votes
2answers
644 views

modify path globally

Is there a standard for $PATH and the order of things that are supposed to be in there? out of the box Arch Linux doesn't have /usr/local/bin in the $PATH. I want to add it but I'm not sure if there's ...
17
votes
6answers
20k views

Grabbing the extension in a file name

How do I get the file extension from bash? Here's what I tried: filename=`basename $filepath` fileext=${filename##*.} By doing that I can get extension of bz2 from the path /dir/subdir/file.bz2, ...
5
votes
1answer
262 views

Whenever I type some wrong command, my terminal tries to run that command in the background

Something strange started happening to my terminal. Whenever I type some wrong command it tries to run that command in the background. hegeek@colinux: ~# l [9]+ Stopped l thegeek@colinux: ~# ...
2
votes
1answer
519 views

Emacs mode in zsh: M-b M-f etc. show weird symbols

I have set up zsh to use emacs mode. But typing Alt+f or Alt+b inserts weird symbols (accented letters and so on), rather than moving around by word in the shell like it should. Since I don't ever ...
1
vote
3answers
258 views

Directory filenames with sed with whitespaces

I'm working on a script and I'm stuck, even with the help of the google. Here's my code: for FOLDER in `find . -type d | sed "s#^.#$(pwd)#" | sed 's/ /\ /g'` do echo "$FOLDER" done This will ...
7
votes
3answers
9k views

How do I change folder timestamps recursively to the newest file?

I was wondering if anyone knows how to change the timestamps of folders recursively based on the latest timestamp found of the files in that folder. So for example: ...
73
votes
9answers
25k views

How do I delete a file whose name begins with “-” (hyphen a.k.a. dash or minus)?

How do you remove a file whose filename begins with a dash (hyphen or minus) -? I'm ssh'd into a remote OSX server and I have this file in my directory: tohru:~ $ ls -l total 8 -rw-r--r-- 1 me ...
2
votes
3answers
998 views

understanding sudoers

I have a unix script which creates a temporary log file, say tempfl.log. When this file is created it has permission rw-r--r--. There is a line chmod 0440 /etc/sudoers tempfl.log 2>&1 But ...
5
votes
1answer
1k views

Is it possible to use named colors in Zsh beyond ANSI names?

I know there are ways to use ANSI color names in Zsh (such as red), but Zsh supports 256 colors by number. I'm curious if there's any way to refer to the non-ANSI colors by a name? (Without just ...
56
votes
5answers
5k views

Redirecting stdout to a file you don't have write permission on

When you attempt to modify a file without having write permissions on it, you get an error: > touch /tmp/foo && sudo chown root /tmp/foo > echo test > /tmp/foo zsh: permission ...
6
votes
2answers
5k views

change prompt color depending on user or root in zsh

in zsh you can have a %# in your PS1 (or whatever PROMPT variable) which basically means display % if user or display # if root. I'm wondering if there is any way to affect this so that the % or # ...
2
votes
1answer
307 views

vi mode doesn't display correctly on new term

This is a continuation of my previous questions. I currently have the following in ~/.zsh.d/functions.sh function zle-line-init zle-keymap-select { psvar[1]="${${KEYMAP/vicmd/}/(main|viins)/-- ...
19
votes
3answers
41k views

How do I switch from an unknown shell to bash?

I was surprised that I didn't find this question already on the site. So, today $ came up after I logged in as a new user. This was unexpected because my main user's prompt starts with ...
5
votes
2answers
2k views

Does cut support non-white-space to white-space delimeters?

The default delimiter in awk is white-space to non-whitespace change. The default for cut is the tab character. Can I tell cut to use non-white-space to white space delimters? E.g. a: foo bar ...
19
votes
5answers
5k views

Why is echo a shell built in command?

$ which echo echo: shell built-in command. $ which ls /bin/ls $ which cat /bin/cat Why is echo not an independent utility like ls, ps, cat etc? Why is it shell specific? Any good reasons?
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votes
3answers
10k views

Convert ascii code to hexadecimal in UNIX shell script

I'd like to convert ASCII code (like - or _ or ., etc.) to hexadecimal representation in the Unix shell (without bc command), eg : - => %2d. Any ideas?
11
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8answers
402 views

How to access the history on the fly in unix?

for example, if I do a mkdir thisismyfolder912 I remember there is some easier way to switch to thisismyfolder912 than having to do a cd thisismyfolder912 What is that way and how does it work? ...
4
votes
2answers
534 views

Scheduling command/script by specifying the exact second

I'm using bash and wondering how I can execute a command/script at a later specified time, with the accuracy of a second? I read the man page for the at-command, but as far as I could understand it's ...
7
votes
2answers
455 views

Stochastic version of seq for generating sequence of random numbers/words?

Some time ago I used a seq-like tool for printing a sequence of pseudo random generated numbers to stdout. You could specify a range, seed, and the number of samples and much more. I've just ...
5
votes
4answers
233 views

is the behaviour of .* to include . and .. defined in LSB or POSIX or some other specification?

as title: is the behaviour of .* to include . and .. defined in LSB or POSIX or some other specification?
21
votes
7answers
4k views

how to glob every hidden file except current and parent directory [duplicate]

I want to glob every hidden file and directory, but not the current (.) and parent directory (..). I am using bash. Observe current behaviour: $ ls -a . .. ...a ...aa ..a ..aa .a .aa .aaa ...
36
votes
10answers
17k views

Batch renaming files

I have a directory full of images: image0001.png image0002.png image0003.png ... And I would like a one-liner to rename them to (say). 0001.png 0002.png 0003.png ... How do I do this?
9
votes
5answers
13k views

Output the common lines (similarities) of two text files (the opposite of diff)?

Diff is a great tool to display the changes between two files. But how to display the similarities of two text files (while ignoring the differences)? I.e. sample input: a: Foo Bar X Hello World 42 ...
13
votes
4answers
23k views

How can I kill a particular thread of a process?

$ ps -e -T | grep myp | grep -v grep 797 797 ? 00:00:00 myp 797 798 ? 00:00:00 myp 797 799 ? 00:00:00 myp 797 800 ? 00:00:00 myp This shows the process ...
3
votes
2answers
719 views

Block specific IP from accessing gateway

Suppose you are on linux internet gateway/router. What would you do to block a client with specific IP using bash script. I prefer something like ./block_client.sh 192.168.1.123 to block and ...
3
votes
3answers
943 views

Is there a way to make the prompt definition multiline?

This is my current prompt definition: PS1=$'%F{063}%1~%f %(1v.%F{099}%1v %f.)%F{063}%%%f ' RPROMPT='$VIMODE %m' and I'm working on integrating this. Basically I'm starting to find it very ...
1
vote
2answers
8k views

Delete files in a directory that match a regexp, using a Mac terminal

How do I delete files in a directory that match a given regexp, or a similar solution, using a Mac terminal?
9
votes
7answers
33k views

Which shell should I use - tcsh vs bash? [closed]

I have been using tcsh for a long time now. But whenever I am searching for something, I often find that the methods specified are bash specific. Even the syntax for the shell scripts is different for ...
13
votes
2answers
3k views

Is there a way to intercept interprocess communication in Unix/Linux?

For intercepting/analyzing network traffic, we have a utility called Wireshark. Do we have a similar utility for intercepting all the interprocess communication between any two processes in ...
23
votes
6answers
70k views

Is there a way to see details of all the threads that a process has in Linux?

For Windows, I think Process Explorer shows you all the threads under a process. Is there a similar command line utility for Linux that can show me details about all the threads a particular process ...
33
votes
7answers
5k views

How to determine where an environment variable came from

I have a linux instance that I set up some time ago. When I fire it up and log in as root there are some environment variables that I set up but I can't remember or find where they came from. I've ...
19
votes
6answers
1k views

How could I remember how to use redirection?

I know what program > /dev/null 2>&1 does. It redirects the output to /dev/null and 2>&1 means to redirect the error output in the same place where the output is sent. My ...
9
votes
1answer
911 views

How do I get a long listing for a single directory?

I want to see a long listing for a single directory. When I type ls -lha, I see this: drwxrwxr-x 4 username groupname 4.0K 2010-08-05 09:55 files drwxrwxr-x 7 username groupname 4.0K 2010-08-05 ...
11
votes
4answers
497 views

rolling diffs for storage of highly similar files?

At work we do a nightly dump of our mysql databases. From day to day, I would guestimate that close to 90-95% of the data is duplicate, increasing as time goes on. ( Heck at this point some are ...