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tomchuk
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Joined: 23 Mar 2003
Posts: 317
Location: Brooklyn, NY
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 Posted: Fri Dec 05, 2003 5:46 pm Post subject: The Non-Annoying Terminal Mini How-To & Fun with shopt |
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I recently posted this to gentoo-user and to my suprise many people had absolutely no idea how to reproduce this error, let alone how to solve it. THis is an essential piece of BASH knowledge that everyone should know.
Broken Line Wraping in Bash
What I'm talking about is the annoying habit BASH has of not checking its window size inbetween commands. To demonstrate, fire up your favorite terminal, and launch a "full screen" app like mutt, nano or less - I'll do "man bash" as it's appropriate to this How-To. Now resize your window to a larger size and quit whatever app you are using. Now try to type a long string.
Instead of:
| Code: | tomchuk@dualie $cat foo | grep bar | awk this | sed that | blah, blah, blah,
blah, blah, blah, blah |
you end up with:
| Code: | | blah, blah, blah, blahoo | grep bar | awk this | sed that | blah, blah, blah, |
The line wraps onto the same line. Not very helpful.
Now try this. Open a terminal as above, and before you do anything type:
| Code: | | shopt -s checkwinsize |
Repeat the steps you took before to induce the weird line wrap. Notice anything different? Now that's how a terminal should behave! What checkwinsize does is force BASH to check the size of the window after the completion of every command - adjusting how large it thinks the terminal is.
To make this system-wide add it to /etc/profile as root:
| Code: | | echo -e 'if [ "$SHELL" = "/bin/bash" ]\nthen\nshopt -s checkwinsize\nfi' >> /etc/profile |
or to make sure your user has this set, add it to ~/.bashrc
| Code: | | echo "shopt -s checkwinsize" >> ~/.bashrc |
More fun with shopt
Alright now that you have your terminal performing at an acceptable level, it's time to play with shopt a little more.
To list the options you have set to 'on':
| Code: | tomchuk@dualie $ shopt -s
checkwinsize on
cmdhist on
expand_aliases on
extglob on
interactive_comments on
login_shell on
progcomp on
promptvars on
sourcepath on
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"shopt -s foo" will set option "foo" to 'on'
To list the options you have set to 'off':
| Code: |
thomas@dualie $ shopt -u
cdable_vars off
cdspell off
checkhash off
execfail off
histreedit off
histappend off
histverify off
hostcomplete off
huponexit off
lithist off
mailwarn off
no_empty_cmd_completion off
nocaseglob off
nullglob off
restricted_shell off
shift_verbose off
xpg_echo off
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"shopt -u foo" will set option "foo" to 'off'
Look at all those options we're not using! I'll cover a couple of the more interesting ones. They're all available in man bash.
cdspell
Ever type "cd /sur/src/linus" or "cd /vat/rmp/postage"? Now you can reinforce your horrible typing with a shell that corrects spelling errors in paths for you.
| Code: |
thomas@dualie $ cd /sur/src/linus
-bash: cd: /sur/src/linus: No such file or directory
thomas@dualie $ shopt -s cdspell
thomas@dualie $ cd /sur/src/linus
/usr/src/linux
thomas@dualie $ ls
COPYING Makefile arch include lib security
CREDITS README crypto init mm sound
Documentation REPORTING-BUGS drivers ipc net usr
MAINTAINERS System.map fs kernel scripts vmlinux
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dotglob
Every want to grep through everything in a directory, or move everything including dotfiles somewhere?
| Code: |
thomas@dualie $ ls -lA
total 0
-rw-r--r-- 1 thomas users 0 Dec 6 13:17 .file
-rw-r--r-- 1 thomas users 0 Dec 6 13:17 file
thomas@dualie $ chmod -r *
thomas@dualie $ ls -lA
total 0
-rw-r--r-- 1 thomas users 0 Dec 6 13:17 .file
--w------- 1 thomas users 0 Dec 6 13:17 file
thomas@dualie $ shopt -s dotglob
thomas@dualie $ chmod -r *
thomas@dualie $ ls -lA
total 0
--w------- 1 thomas users 0 Dec 6 13:17 .file
--w------- 1 thomas users 0 Dec 6 13:17 file
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This sure beats "chmod -r .* *" as ".*" includes "." which will remove write permissions from the current directory as well as all the dotfiles in it - not good.
Last edited by tomchuk on Mon Dec 08, 2003 5:47 am; edited 4 times in total |
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genneth
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Joined: 24 Mar 2003
Posts: 152
Location: UK
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| Posted: Fri Dec 05, 2003 6:02 pm Post subject: |
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yes...!!!! |
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ikokai
n00b
Joined: 10 Nov 2003
Posts: 14
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| Posted: Fri Dec 05, 2003 6:10 pm Post subject: |
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| Thanks, I always wondered how to get rid off this. |
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marshall_j
Tux's lil' helper
Joined: 22 Jan 2003
Posts: 98
Location: NZ
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| Posted: Fri Dec 05, 2003 9:38 pm Post subject: |
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| cheers for that. that always annoyed me!! |
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twiggy
n00b
Joined: 25 Nov 2003
Posts: 65
Location: Sweden
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| Posted: Fri Dec 05, 2003 10:04 pm Post subject: |
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| yey.. that has been bugging me quite some time now, thanks |
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castorilo
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Joined: 25 Dec 2002
Posts: 157
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| Posted: Fri Dec 05, 2003 10:27 pm Post subject: |
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| Thanks. I was always annoyed by this and had no clue on how to reproduce this or fix it. |
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neenee
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Joined: 20 Jul 2003
Posts: 1786
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| Posted: Fri Dec 05, 2003 11:40 pm Post subject: |
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thanks  |
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Unne
l33t
Joined: 21 Jul 2003
Posts: 616
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| Posted: Sat Dec 06, 2003 2:00 am Post subject: |
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| That's really great. I always thought that bash quirk was just something I had to live with. |
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Jeedo
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Joined: 02 May 2003
Posts: 202
Location: Akureyri, Iceland
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| Posted: Sat Dec 06, 2003 2:03 am Post subject: |
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| same here, thx. |
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Halanegri
Guru
Joined: 03 Mar 2003
Posts: 351
Location: Reykjavík, Iceland
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| Posted: Sat Dec 06, 2003 2:27 am Post subject: |
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| Unne wrote: | | That's really great. I always thought that bash quirk was just something I had to live with. |
same here |
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X
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Joined: 30 Apr 2002
Posts: 192
Location: Lexington KY
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| Posted: Sat Dec 06, 2003 3:23 am Post subject: |
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| Happy day. |
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verbatim
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Joined: 13 Mar 2003
Posts: 223
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| Posted: Sat Dec 06, 2003 5:37 am Post subject: |
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Very cool.  |
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Config
Retired Dev
Joined: 25 May 2003
Posts: 187
Location: Zurich, Switzerland
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| Posted: Sat Dec 06, 2003 1:44 pm Post subject: |
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Wow, this is just awesome - thank you a lot!
Now I can come back and enjoy pine
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Config - caught by a chronic disease called tuxmania.... |
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grzewho
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Joined: 31 Dec 2002
Posts: 626
Location: /home/g
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| Posted: Sat Dec 06, 2003 5:29 pm Post subject: |
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this line should get to the official gentoo /etc/profile (dunno if it`s baselayout`s or bash`s file)
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| Code: | | USE="freedom -software_patents" emerge --deep --update world |
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viperlin
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Joined: 15 Apr 2003
Posts: 1319
Location: UK
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| Posted: Sat Dec 06, 2003 8:30 pm Post subject: |
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thanks that bash thing annoyed the hell out of me  |
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ikaro
Advocate
Joined: 14 Jul 2003
Posts: 2527
Location: Denmark
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| Posted: Mon Dec 08, 2003 3:49 am Post subject: |
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bupping this up, Thanks !
gotta love these fixes 
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jesterspet
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Joined: 05 Feb 2003
Posts: 215
Location: Atlanta
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| Posted: Mon Dec 08, 2003 4:42 am Post subject: Re: The Non-Annoying Terminal Mini How-To & Fun with sho |
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| tomchuk wrote: | | To make this system-wide add it to /etc/profile as root |
Um.. shouldn't this be added to /etc/bashrc instead of /etc/profile 
Since this is bash specific, and not relevant to other shells, it really doesn't belong in /etc/profile .
I cannot remember if /etc/bashrc is included in a default install, or if the check to see if it exists is included in /etc/skel/.bashrc (or ~/.bashrc) so just for the sake of completeness, I'll point out that copying & editing the one that checks for /etc/profile in ~/.bashrc works just fine.
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tomchuk
Guru
Joined: 23 Mar 2003
Posts: 317
Location: Brooklyn, NY
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| Posted: Mon Dec 08, 2003 6:06 am Post subject: Re: The Non-Annoying Terminal Mini How-To & Fun with sho |
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Glad everyone is enjoying this
| jesterspet wrote: | | Um.. shouldn't this be added to /etc/bashrc instead of /etc/profile |
Good catch, thanks.
I agree it shouldn't be in /etc/profile as it was, but I don't believe that gentoo's bash install looks at /etc/bashrc - it's not mentioned in the man page and I couldn't make it happen, short of adding "source /etc/bashrc" to my ~/.bashrc which defeats the purpose. I added an if statement that checks $SHELL before issueing shopt which does the trick. |
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Krigare
Tux's lil' helper
Joined: 12 Nov 2003
Posts: 92
Location: ::1
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| Posted: Mon Dec 08, 2003 9:06 am Post subject: |
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this is just perfect
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tarzan420
Tux's lil' helper
Joined: 05 Jul 2003
Posts: 81
Location: Fairbanks AK
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| Posted: Wed Dec 10, 2003 5:58 pm Post subject: Screwy Word Wrap because of ANSI Colors? |
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| I had gotten the impression that the word wrap problems had to do with ANSI colors in the bash profile (You know, green/red username, blue path). I came to this conclusion after I read more about them in a recent GWN, and then tried to use the colors for my prompt on my debian box. While the color worked, I still had strange line wrapping problems. Cause and Effect? I'm not sure. |
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tomchuk
Guru
Joined: 23 Mar 2003
Posts: 317
Location: Brooklyn, NY
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| Posted: Wed Dec 10, 2003 8:00 pm Post subject: |
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Like you said, weird line wraps can also be caused by improperly escaped prompts (PS1). For every non-printing character (color codes, etc) you must escape them with \[ and \].
A simple colored PS1:
| Code: | | PS1='\033[01;34m\u@\033[01;31m\h \$' |
That will cause weird line wrapping because when calculating the window width and the length of the prompt bash considers the color codes as priniting characters. The solution is to escape the color codes like:
| Code: | | PS1='\[\033[01;34m\]\u@\[\033[01;31m\]\h \$' |
Try each of those and you'll find that the first will wrap the line weirdly but the second is just fine. |
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OneOfOne
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Joined: 28 May 2003
Posts: 368
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| Posted: Sat Dec 13, 2003 7:47 pm Post subject: |
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| awesome! |
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rhill
Retired Dev
Joined: 22 Oct 2004
Posts: 1629
Location: sk.ca
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| Posted: Sun Nov 28, 2004 1:05 pm Post subject: |
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bump.
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by design, by neglect
for a fact or just for effect |
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SaFrOuT
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Joined: 08 Jul 2003
Posts: 256
Location: Egypt
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| Posted: Sun Nov 28, 2004 2:47 pm Post subject: |
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although it is an old thread but it was very helpful
thanks dirtyepic for bumbing it
and SURE thanks tomchuk |
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zsoltika
l33t
Joined: 13 Nov 2003
Posts: 634
Location: Budapest, Hungary
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| Posted: Mon Nov 29, 2004 6:17 am Post subject: Re: The Non-Annoying Terminal Mini How-To & Fun with sho |
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Hi guys,
I followed this steps:
| tomchuk wrote: |
Broken Line Wraping in Bash
What I'm talking about is the annoying habit BASH has of not checking its window size inbetween commands. To demonstrate, fire up your favorite terminal, and launch a "full screen" app like mutt, nano or less - I'll do "man bash" as it's appropriate to this How-To. Now resize your window to a larger size and quit whatever app you are using. Now try to type a long string.
Instead of:
| Code: | tomchuk@dualie $cat foo | grep bar | awk this | sed that | blah, blah, blah,
blah, blah, blah, blah |
you end up with:
| Code: | | blah, blah, blah, blahoo | grep bar | awk this | sed that | blah, blah, blah, |
The line wraps onto the same line. Not very helpful.
Now try this. Open a terminal as above, and before you do anything type:
| Code: | | shopt -s checkwinsize |
Repeat the steps you took before to induce the weird line wrap. Notice anything different? Now that's how a terminal should behave! What checkwinsize does is force BASH to check the size of the window after the completion of every command - adjusting how large it thinks the terminal is.
To make this system-wide add it to /etc/profile as root:
| Code: | | echo -e 'if [ "$SHELL" = "/bin/bash" ]\nthen\nshopt -s checkwinsize\nfi' >> /etc/profile |
or to make sure your user has this set, add it to ~/.bashrc
| Code: | | echo "shopt -s checkwinsize" >> ~/.bashrc |
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but after this I still end up whit messed up command line 
I mean, using this | Code: | export PS1="[\e[31m\$(pwd)\e[0m :: \e[32m\@\e[0m :: \e[33m\l\e[0m]\n[\e[32m\u\e[
0m@\e[34m\H\e[0m] \$ " |
I still end up with command lines like this: | Code: | | aaaaaaaaaaaaaaaaaaaaaaa'ss prova_a0.svg | grep 'aaaaaaaaaaaaaa |
I'm using Xterm(196) and GNU bash, version 3.00.13(1)-release (i686-pc-linux-gnu).
Any idea?
Thx,
Zsoltika |
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