Assign conditional test to variable?

I want to assign the result of a conditional test to a variable. How do I accomplish in bash?

I understand if syntax

if some_condition

I don't know how to move that into a variable

# Does this work?
$variable=some_condition

https://redd.it/zi0ddk
@r_bash

Is there a way to alias a global disabling of all bash functions for a single command?

So, the reason I ask this is because I got tired of not being able to do math in the command line so I made a python noscript called math that, well, does math. But the problem is I have to quote everything for bash to not complain, and it's super frustrating. Already I'm missing quotes all the time and having to redo things.

An example is to evaluate the number 123 into binary. I can now type math bin(123). But then I get a bash: syntax error near unexpected token '('. Similarly with say math round(34 + sqrt(13), 2). You get the picture.

I've looked and I can't find anything clear on this. Is there anyway to do this? I suspect not but I want to ask because it would be so amazing. Something where I can alias, in pseudocode: turn off all bash reading of things; read input line; pipe to math noscript; turn back no bash reading of things. I guess what I'm really asking for is a way to really just take the input string as raw, with nothing else to it.

Thank you! I totally understand if the answer is "impossible", I just want to exhaust all options before resigning myself to quote hell.

Edit: fixed markdown.

https://redd.it/zi1z9e
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Comparing CPU features with the help of cut/tr/diff/grep commands
https://yurichev.org/tr/

https://redd.it/zi55f0
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dext: Sort files into directories based on file extensions
https://github.com/AfzGit/dext

https://redd.it/zi477o
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How to convert a txt file to one line with escape characters

I'm trying to make my text file look like this:

test\nim a new line\nso am i!


instead of this


test
im a new line
so am i!

How can I do that in the command line of bash?

All help is appreciated, thank you!

https://redd.it/zi66z2
@r_bash

How do I read a variable to replace it with a placeholder?

Assume I have the following in my noscript file:

export myvar=placeholder

I want to run the noscript and be asked the value of the $myvar, and then have it fill and replace the word "placeholder".

Any suggestions? I don't have to have the word "placeholder" I can leave it blank, if it is easier.

https://redd.it/zi3z5x
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Newbie in bash noscript

How to send a picture with notification with a button working I tried notify-send but can't make a button using that.

https://redd.it/ziewvs
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How to send a picture with notification with a button working I tried notify-send but can't make a button using that.



https://redd.it/zig8a8
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Shell toolkit alternative without overlapping functionality

Is there similar to sed, awk, grep, cut and other similar tools without overlapping functionality? I need some set of atomic commands each doing one task, not several, just one. I prefer readability over short syntax also. It means that I prefer awk instead of sed. When I use cat, grep I feel that it's pointless in some way as they do what awk can. By all means, it's faster to use grep or cat to search smth or print file contents respectively. But it leads to the problem where you memorize more commands and know less about each of them, you spread all your energy on several commands instead of learning few deeply.

https://redd.it/zik3el
@r_bash

Why use the test command?

Over the last few days I've seen comments suggesting that the OP use test. I see some examples like:

if test -f "$1"; then

But what advantages does that have over using:

if [ -f $1 ]; then

When would you need "if test" instead of "if"?

https://redd.it/zimjju
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linecomp: fish-style autosuggestions in bash!

https://redd.it/ziwzac
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How to make yq to produce nothing for missing keys instead of null?

I wanna load my yaml based config in my bash noscript via yq like this:

corefunctionloadmessagecolordefaults() {
INFOCOLOR="${INFOCOLOR:-green}"
WARNCOLOR="${WARNCOLOR:-yellow}"
ERRORCOLOR="${ERRORCOLOR:-red}"
}

declare configname="$HOME/bash-settings.yml"

if ! which yq > /dev/null; then
warn "no 'yq' command found to load info, warn, error colors; defaults have been loaded"
corefunctionloadmessagecolordefaults
elif [[ ! -e "$configname" ]]; then
warn "no '$configname' file found to load info, warn, error colors; defaults have been loaded"
corefunctionloadmessagecolordefaults
else
INFOCOLOR="$(yq ".messages.info.foreground" "$configname")"
WARNCOLOR="$(yq ".messages.warn.foreground" "$configname")"
ERRORCOLOR="$(yq ".messages.error.foreground" "$configname")"
corefunctionloadmessagecolordefaults # Some value can be missing in config in which case default value must be used.
fi

unset configname


But the problem is when I yq encounters missing keys in $config_file it prints null. By all means I can change my code to check whether variable's value is "null" string and then set it to default if it's true but I don't like this decision and unsure whether there is smth better.

https://redd.it/ziymto
@r_bash

Xargs does not accept input piped from cut

Hi there, I'm trying to understand why xargs does not echo some input, when piped from the cut command.


I have this bash noscript:
\#!/bin/bash

inotifywait -qme create,moved_to /path/to/directory | xargs -I{} echo '{}'


\# end noscript

When I run this noscript, and copy (or move) a file to the said directory, I get ouptput like this: "/path/to/directory CREATE filename" (as expected)

​

​

​

However, when I edit this so cut removes the two first words (to leave only the filename), it seems xargs does not recognize the piped input.
This:

inotifywait -qme create,moved_to /path/to/directory | cut -d' ' -f3- | xargs -I{} echo '{}'

outputs nothing when a file is copied or moved into said directory - my expectation is that it would echo the filename.

Why is this?


​

​

I realize I could easily remove xargs from this command entirely, and it would output the filename. The final goal however is to remove the file from the folder in question, e.g inotifywait -qme create,moved_to /path/to/directory | cut -d' ' -f3- | xargs -I{} rm /path/to/directory{}.


Thusly, I'll need to understand how to pipe the filename from cut to xargs.


​

​

I have the same issue with other commands, for example, I tried

awk '{for(i=6;i<=NF;i++){printf $i" "}print ""}'

instead of cut - this also failed to get xargs to echo anything. instead of cut, i'd be fine with using sed, grep, awk, etc to remove the first two words from the output of inotifywait - as long as it can be successfully piped into xargs

https://redd.it/zj1kfi
@r_bash

Soo ChatGPT can basically write noscripts for you... Thoughts?

&#x200B;

https://preview.redd.it/n1b6hm1cia5a1.png?width=625&format=png&auto=webp&s=92f48df624233147bddd52ffb1392802855c1281

https://redd.it/zix2am
@r_bash

Bash Scripting vs Shell Scripting

If I learn Bash noscripting, is it pretty straight forward to learn how to write shell noscripts? How difficult is it to convert those bash noscripts to other *unix like shells (zsh, awk, fish)? What are some of the major differences to be aware of?

https://redd.it/zjf220
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Help me understand the unclear language of the "locate" man, please

The command in question is "locate" in bash 3.2 on macOS. The fragments I have an issue with are the following:

> Shell globbing and quoting characters ('', ``?'', ``\'', ``['' and ``]'') may be used in pattern, although they will have to be escaped from the shell. Preceding any character with a backslash (``\'') eliminates any special meaning which it may have. The matching differs in that no characters must be matched explicitly, including slashes (``/'').

1. Since I haven't read man pages for a long time I forgot the symbolic meaning of the notation used. Why does the man page put double single quotes around these special characters? Are those the actual , ? ... or *'. ?' ...?
2. Does the part saying that "they will have to be escaped from the shell" imply the double single quotes or the backlash character it brings in the next sentence?
3. "The matching differs in that no characters must be matched explicitly…": differs from what? "no chars must be matched explicitly" by whom or by what or in what context? Why "must" and not "have to"? What does "matched explicitly" mean? I can't have literal matches?

Another foggy excerpt is this:

> The 8-bit character support does not waste extra space for plain ASCII file names.

How is it "doesn't waste" and what would be it like if it did?

https://redd.it/zjk0un
@r_bash

Having fun with bind shells and named pipes!

#!//usr/bin/bash

#BIND SHELL WITH NAMED PIPES
#CREATED BY: Zerodark875

fail() { ecode=${1};shift; 2>&1 echo "${*}";exit ${ecode};}
usage() { echo -e "Create bind shells using netcat and named pipes.\n\nUsage: $(basename ${0}) [port]\n\t[port]\t\tTCP Port number to listen on\n\t-h, --help\tThis Help Menu";fail 1;}
cleanup() { if [[ -e ${1} ]]; then echo "Cleaning up. Deleting ${1}"; rm -f ${1};fi;}

if [[ -z ${1} ]] || [[ ${1,,} == "-h" ]] || [[ ${1,,} == "--help" ]]; then
usage
fi

NP="/tmp/net_shell"
PORT=${1}

echo -n "Are you sure you want to start a bind shell on port ${PORT} (N/y):"
read choice
if [[ ${choice,,} == "n" ]]; then
fail 0 "Done."
fi

cleanup ${NP}

mkfifo ${NP} #make out named pipe!

echo "Starting bind shell on port ${PORT}"
cat ${NP} | $(which bash) -i 2>&1 | nc -nlp ${PORT} > ${NP}

cleanup ${NP}
echo "Done."

https://redd.it/zjql2p
@r_bash

Add Header to csv file if no header is present

Hello!

What would be the best approach for trying to add header to a csv file, only if that file doesn’t contain the header?

What I was thinking was to get the first row, check wether it is the header, and if not add the header, but I am curious if there are other approaches.

Thanks in advance!

https://redd.it/zjqzj5
@r_bash

How to proper escape characters to to output string with color codes (non interpreted yet)?

Hi! I have the following code:

awk "{ print gensub(/\"(^ +)\"/, \"\\$(rawforeground magenta)\\\\1\\$(rawforeground none)\", \"g\") }" <<< ' "some" '

raw_foreground returns smth like \e[{{some-number}}m:

rawforeground() {
[[ -n "$2" ]] && {
corefunctionfailurewithinvalidargumenterror
return $FAILUREWITHINVALIDARGUMENT
}

declare colorname="$1"
declare -A colornameassociations=(
[none]=0
[black]=30
[red]=31
[green]=32
[yellow]=33
[blue]=34
[magenta]=35
[cyan]=36
[light-gray]=37
[gray]=90
[light-red]=91
[light-green]=92
[light-yellow]=93
[light-blue]=94
[light-magenta]=95
[light-cyan]=96
[white]=97
)

[[ ! -v colornameassociations[$colorname] ]] && {
corefunctionfailurewithinvalidargumentoutofrangeerror "${!colornameassociations[@]}"
return $FAILUREWITHINVALIDARGUMENTOUTOFRANGE
}
echo -n "\e[${colornameassociations[$colorname]}m"
}

I wanna replace "some" with "\e[45msome\e[0m" but I don't understand what I am missing now in the context of escaping characters.

https://redd.it/zjxctf
@r_bash

Testing if array elements are inside a string, not working when using *

Hi there

I'm stuck, tried a bunch of stuff & just can't work it out, would really appreciate some help!

I have an array, containing key words/phrases that can be contained in denoscription fields, if the denoscription field I'm handling contains one of these then I want to react in a certain way.

An example of my problem. I'm maybe misunderstanding how the [*\] bit works on arrays, don't know, but I'm expecting this to give the same results - as you can see, it doesn't! It looks like it should be so simple, & I really don't want to have to cycle through each element of the array 1 by 1:

# ignore_denoscription=("CHECK_NRPE" "Return code of 255" "Service check timed out after" "Plugin timed out" "(No output on stdout) stder" "(No output on stdout) stder")

# denoscription="This is an example containing CHECK_NRPE just to test"

# if [[ ${denoscription} =~ ${ignore_denoscription[0]} ]] ; then echo "it's there"; fi

it's there

# if [[ ${denoscription} =~ ${ignore_denoscription[*]} ]] ; then echo "it's there"; fi

#

Really appreciate any help!

https://redd.it/zk5yzk
@r_bash

Optimal par2 Switches for Mixed Data

I have compressed many files using bash find-exec tar.xz. I'd like to protect it for storage with ECCs. Data is mixed -- images, text, docs, html & associated folder .. & assorted media and zip files. I plan to create directories -- say, 1 to 10mb -- & compress. Then put each file in its own directory along with its ECCs.
find . -type f -name "*.tar.xz" -exec par2 create -s 1k -n 3 -r 10 "{}" ;
That's my noscript so far, guessing at appropriate block size, number of ECC files, & percent redundancy. I can't find good examples on how to set parameters with variant data. Suggestions much appreciated !!

https://redd.it/zk9zwe
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