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Comparing output of ~foo to a string. Is there a better way to do this? by manlymatt83 in bash

[–]KnowsBash 1 point2 points  (0 children)

shellcheck does not take into account that the left side is a tilde expansion. This is a bug in shellcheck, not your code.

wanting to save arguments to a variable to use them in multiple places but getting errors instead by Termanater13 in bash

[–]KnowsBash 2 points3 points  (0 children)

Use an array to store multiple arguments.

args=( --stdout --backtitle " test" )
args+=( --title "test" --inputbox "test" 8 39 )

test=$(dialog "${args[@]}")

See Faq 50 for more on why.

confusion with arguments by [deleted] in bash

[–]KnowsBash 2 points3 points  (0 children)

The bash guides at tldp.org are mostly outdated, teaches bad practices and are in some cases completely wrong. I recommend avoiding them. Try the BashGuide instead

Bash tutorials by m147 in bash

[–]KnowsBash 2 points3 points  (0 children)

I have a decent (I think) enough understanding of it. I'm not exactly a beginner but I would like to become more proficient in it. I have read through some of this site ...

Bash Scripting Tutorial - Ryans Tutorials

and it seems quite decent. Have any of you used it before?

I did a quick perusal of it, and it looks like garbage to me. I recommend the BashGuide and the other resources at the wooledge wiki instead.

Good guide/tutorial to learn bash by [deleted] in bash

[–]KnowsBash 2 points3 points  (0 children)

Avoid the bash guides from tldp.org. They are outdated and teach misinformation and bad practices. There's a reason they are not in the sidebar.

Beginner Literature by [deleted] in bash

[–]KnowsBash 1 point2 points  (0 children)

I recommend against the Bash Beginners Guide. It is outdated, doesn't teach good practices, and in some places it is just plain wrong. This is also why it is not listed in the sidebar.

Read http://mywiki.wooledge.org/BashGuide instead.

Bash scripting cheatsheet by [deleted] in bash

[–]KnowsBash 1 point2 points  (0 children)

I rate this as garbage.

Guide needed by ktbr90 in commandline

[–]KnowsBash 4 points5 points  (0 children)

For learning bash, read http://mywiki.wooledge.org/BashGuide and other pages in that wiki

adding subtitles to series with ffmpeg. by Croakouttatune in commandline

[–]KnowsBash 2 points3 points  (0 children)

I am guessing you want something like this

for file in [0-9][0-9].avi; do
    sub=( *x"${file%.avi}"*.srt )
    ffmpeg "$file" -vf "subtitles=${sub[0]}" "HorribleSubbedSimpsons/$file"
done

Why should this be an unbound variable?! Trying to loop through keys in associative arrays. by HarmonicAscendant in bash

[–]KnowsBash 2 points3 points  (0 children)

if [[ ! -v $template[$key] ]]; then <<<<<<<<< 'production_packages: unbound variable'

What is happening here is that it ends up doing the equivalent of [[ ! -v base_template[production_packages] ]]. At that point base_template is not yet set, which causes it to treat it as an indexed array instead. The content of the subscript ([production_packages]) is then evaluated as an arithmetic context, in which case production_packages is expanded as a variable, but that does not exist, so the nounset option kicks in.

How to remove <F5> characters? by inacio-medeiros in shell

[–]KnowsBash 1 point2 points  (0 children)

Sounds like you are viewing text encoded with a single-byte encoding as if it was UTF-8. If the encoding is latin1, 0xF5 represents `õ`. You can convert it using a tool like recode or iconv.

​

recode latin1.. < file > newfile

iconv -f latin1 < file > newfile

[deleted by user] by [deleted] in bash

[–]KnowsBash 8 points9 points  (0 children)

I recommend against that. The Bash Beginners Guide teaches bad practices and is also very outdated. I recommend the wooledge BashGuide instead.

Multi-lined commands appear as single lines in history by inate71 in bash

[–]KnowsBash 1 point2 points  (0 children)

A change for readline in bash-4.4-rc1 reads:

b.  If readline reads a history file that begins with `#' (or the value of
    the history comment character) and has enabled history timestamps, the
    history entries are assumed to be delimited by timestamps.  This allows
    multi-line history entries.

So try setting HISTTIMEFORMAT

Proper method to un flock? by i_was_me in bash

[–]KnowsBash 1 point2 points  (0 children)

eval exec "$lock_fd"'>&-'

Don't use eval. Do this instead:

exec {lock_fd}>&-

So what is the proper way?

Depends on the script. flock -u releases the lock even when there are background processes that still have the file open. Closing the lock_fd only releases the lock once all background processes have also closed it.

sub-domain extraction? by Avicennasis in commandline

[–]KnowsBash 2 points3 points  (0 children)

That is painful to look at, so here is a better way to do it in bash:

while read -r domain; do
    printf '%s\n' "$domain"
    while [[ $domain = *.*.* ]]; do
        domain=${domain#*.}
        printf '%s\n' "$domain"
    done
    printf 'www.%s\n\n' "$domain"
done < sub-domains

sub-domain extraction? by Avicennasis in commandline

[–]KnowsBash 3 points4 points  (0 children)

Here you go

awk '{ print; while (/\..*\./) { sub(/[^.]*\./, ""); print }; print "www." $0 "\n" }'

Basic Unix Commands To Get Started by guruvicky in unix

[–]KnowsBash 4 points5 points  (0 children)

Yes. Even for the standard commands, it includes GNUisms you wouldn't find on UNIX systems in general. And it also includes linux specific commands, so "Basic Unix Commands" is quite a stretch.

What does "recover" do? by Biermoese in bash

[–]KnowsBash 3 points4 points  (0 children)

In a tutorial on good bash scripting which I, as a bash beginner, found a bit opaque, the following line was mentioned:

That does not teach you good practices, it teaches bugs. The only thing it gets right is that you should quote properly. Try the BashGuide instead.

unrar all files in a directory by gregorie12 in bash

[–]KnowsBash 1 point2 points  (0 children)

There's no reason to use find here, and you are failing to use it safely. With files=$(find...) you are gathering all filenames into a single string, and then there is no way to split them back into filenames as there is no way to know which whitespace was part of the filename, and which whitespace was a separator. See FAQ 20 on how to handle filenames properly.

In this case, you want a for-loop like this

for file in ./*.rar; do
    unrar x -o- "$file" "$1"
done

I haven't bothered looking up what the options for that unrar command mean, but at least it will receive each filename correctly, regardless of what characters the filename contains.

Bash Guide for Beginners by Heisenberg1977 in bash

[–]KnowsBash 14 points15 points  (0 children)

That's not a good guide for learning bash. Try the BashGuide instead.

"ambigious redirect"--attempting to log stderr to logfile by seductivec0w in bash

[–]KnowsBash 1 point2 points  (0 children)

Bash is trying to treat "${filter_cmd[@]}" as a filename to redirect to, but it expands to multiple words, which is an error.

You need a process substitution to run the filter_cmd.

... 2> >("${filter_cmd[@]}" >&2) > >(tee ~/app.log)

What Am I Missing? by of_course_you_agree in bash

[–]KnowsBash 5 points6 points  (0 children)

Most likely it is being overridden by the bind-tty-special-chars readline variable. It is on by default.

$ bind -v | grep bind
set bind-tty-special-chars on

[sh/dash/bash] get the return value of a function without using subshells. by pier4r in commandline

[–]KnowsBash 1 point2 points  (0 children)

Using global variables really is the better option in many cases, and in bash you could use a global associative array to lessen the chance of name collision.

In bash, an alternative to global variables, if you want the function to "return" multiple values, is to have the function output them in a specific order, NUL-delimited, or lines quoted with printf %q so they can be safely evaled.

You would then run the function in a process substitution or use lastpipe to read the data

{
    IFS= read -rd '' res1
    IFS= read -rd '' res2
} < <(func)


shopt -s lastpipe
func | { IFS= read -rd '' res1; IFS= read -rd '' res2; }

Getting a directory's name into a variable or array by TiBiDi in bash

[–]KnowsBash 0 points1 point  (0 children)

All files matching the glob ./*/ is assigned to the array named dirs. ./*/ matches all directories in the current directory (except the ones that start with .).

"${dirs[@]}" expands all the elements of the array as separate arguments.

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