[Discussion/Diversion] Convenience shell tips and tricks for Slackware users.

fourtysixandtwo · 12-26-2022, 09:28 PM

This thread is a great idea. Here's a few I use adapted to use the same PKGDIR variable.

Code:

PKGDIR="/var/lib/pkgtools/packages"

# list kernel pkgs natural sort
kernsort () {
  ( cd $PKGDIR ; ls -lv kernel-* )
}

# list kernel pkgs grouped by version
kernsortver () {
  ( cd $PKGDIR ; ls kernel-* ) | sort -t- -k3
}

# get list of installed slackbuilds (_SBo tag) that no longer exist in repo
SLACKBUILDS=/var/lib/sbopkg/SBo/15.0/SLACKBUILDS.TXT
#SLACKBUILDS=/usr/sbo/repo/SLACKBUILDS.TXT
#SLACKBUILDS=/var/lib/slpkg/repository/SLACKBUILDS.TXT

sbremoved () {
  for i in `( cd $PKGDIR ; ls *_SBo ) | rev |cut -d- -f4-|rev`
  do
    echo -n "$i "
    grep -c "SLACKBUILD NAME: $i$" $SLACKBUILDS
  done | grep 0$
}

pan64 · 12-27-2022, 04:13 AM

Quote:

Originally Posted by 0XBF

@pan64

The idea behind this thread was to generate some discussion around convenience functions or scripts that users have cooked up over the years to help manage, troubleshoot, or speed up any other menial tasks on their Slackware system.

It is in general a very good idea.

Quote:

Originally Posted by 0XBF

These ideas are not going into the distribution, they were just talking points that I was trying to use to spark some ideas or conversation. I'm just another Slackware user and not making development decisions for anyone.

When you post them and show them (not exactly you, but anyone), it means you want to add something to slackware (but in general to any distro). it's a helpful tool, and it's meant to be useful for more than just you (oh yes, you did make development already). Which is totally fine really.
And now comes the interesting part: do you want to share low quality, slow and resource hungry code just because you don't really care about that 1 sec?

Quote:

Originally Posted by 0XBF

I got your point about inefficiencies of using sub-shells so lets not beat a dead horse about perfect coding practices because that's not what I wanted to discuss.

And this is the next step: I [tried to] improve your code by discussing that issue, because I care about it. Is it a common goal, isn't it?

Quote:

Originally Posted by 0XBF

If there's no interest in the topic as I originally posed in post #1 then I'm fine letting it die off without the arguing over how people should write their bash scripts. If I wanted better efficiency I would write something in C, not bash, but that's not the point here.

That is just wrong, you can write high and low quality code on any language. Obviously discussing the quality of the scripts is [almost] offtopic here, but a very important question. For my part, I would do my best if I wanted to give (share) anything to others.

Windu · 12-27-2022, 04:47 AM

Quote:

Originally Posted by pan64

That is just wrong, you can write high and low quality code on any language. Obviously discussing the quality of the scripts is [almost] offtopic here, but a very important question. For my part, I would do my best if I wanted to give (share) anything to others.

Code can be written less than optimally if that has a purpose, which is that of understanding and readability. Otherwise, everybody should just write assembler code, right? Including you.

Bindestreck · 12-27-2022, 05:53 AM

I side up with @pan64 here. Why everyone feels buttfucked when @pan64 clearly just try to give advice on how to further improve the code? Why is that bad?

Windu · 12-27-2022, 06:21 AM

Quote:

Originally Posted by Bindestreck

I side up with @pan64 here. Why everyone feels buttfucked when @pan64 clearly just try to give advice on how to further improve the code? Why is that bad?

I have no issue with his suggestions for improving the example code snippets, they are good. I was triggered by his remark "Wasting resources is a bad habit. It does not hurt as long as your box has no real task to do. You can do what you want for yourself, but for such a community, this is not an example to follow".

0XBF · 12-27-2022, 09:44 AM

Quote:

Originally Posted by pan64

And now comes the interesting part: do you want to share low quality, slow and resource hungry code just because you don't really care about that 1 sec?

Context matters here. A scenario where I use these generally goes like this: 1. I find a library or file or something and wonder where it came from, so I 'pkggrep' it. If I want to look further at that package I 'pkgcat' into a pager and read it. Execution time doesn't matter for my case and I'm not calling the function with heavy usage from another script or anything. My aim was that it made it quicker than writing out the full "cat <full pathname>" to examine a package, and that was about it.

Quote:

Originally Posted by pan64

Obviously discussing the quality of the scripts is [almost] offtopic here...

Exactly the point I was trying to make. I wasnt trying to just talk about the most efficient way to do my pkgcat function and I didnt want the topic to get "buried in the weeds" over that. I appreciate your suggestions for improvements, but then devolving into back and fourth about wasting resources and doing things "the MS way" kinda derails the topic of getting others to share their own scripts/functions, so I was trying to nip it in the bud. I hope you understand where I'm coming from.

gegechris99 · 12-27-2022, 11:45 AM

I have a script that checks for update of Slackware or third-party package repositories (I'm using slackpkg+).
The script runs every hour using cron and sends a desktop notification when the Slackware or a third-party repository has any update.
To be able to send a desktop notification (to fluxbox), I need to export the session DBUS_SESSION_BUS_ADDRESS variable before executing notify-send.
The way I get DBUS_SESSION_BUS_ADDRESS variable could probably be improved but as stated by OP, it's not the primary topic to be discussed here.
However, I'm open to suggestion (maybe in PM to avoid being off-topic).

Code:

$ crontab -l
SHELL=/bin/bash

# Check update of Slackware packages
# minute | hour | day of month | month | day of week
0 * * * * sh $HOME/data/script/check_slackware_update.sh

Code:

$ cat $HOME/data/script/check_slackware_update.sh 
#!/bin/bash
/usr/sbin/slackpkg &>/dev/null check-updates
username=$(/usr/bin/whoami)
export $(ps -u $username e | grep -m 1 -Eo 'DBUS_SESSION_BUS_ADDRESS=[^ ]* ')
[ -s ~/.slackpkg/updated-repos.txt ] && /usr/bin/notify-send -i dialog-warning "[ S L A C K P K G + ]" "Available updates in repositories: $(cat ~/.slackpkg/updated-repos.txt|tr '\n' ','|sed 's/,$//')"

metaed · 12-27-2022, 06:05 PM

Quote:

Originally Posted by gegechris99

I have a script that checks for update of Slackware or third-party package repositories

I do something similar but without notifications. I depend on cron to mail me the update. The core tool is:

Code:

#! /bin/sh
# Compiled from slackcheck.nw using Noweb by Norman Ramsey.
cd /var/lib/slackcheck
id=$(sed -n '/^ID=\(.*\)$/ s//\1/p' /etc/os-release)
case "$id" in
slackware)  server=ftp://ftp.slackware.com/pub ;;
*)      echo slackcheck: id="$id" not yet supported by slackcheck
        exit 1
esac
case $(uname -m) in
i[3456]86)     archpath=slackware/slackware ;;
[xX]86[_-]64)  archpath=slackware/slackware64 ;;
*)      echo slackcheck: $(uname -m) architecture not yet supported by slackcheck
        exit 1
esac
version=$(sed -n '/^VERSION="\(.*\)"$/ s//\1/p' /etc/os-release)
codename=$(sed -n '/^VERSION_CODENAME=\(.*\)$/ s//\1/p' /etc/os-release)
case $codename in
current) changelog=$server/$archpath-current/ChangeLog.txt ;;
stable)  changelog=$server/$archpath-$version/ChangeLog.txt ;;
*)      echo slackcheck: this /etc/os-release not yet supported by slackcheck
        exit 1
esac
wget -Nq $changelog
laststamp=` 2>/dev/null cat ChangeLog.stamp `
thisstamp=` 2>/dev/null head -1 ChangeLog.txt `
if [ "$thisstamp" = "" ]
then    echo slackcheck: failed to get timestamp
        exit 1
elif [ "$laststamp" = "" ]
then    echo 'slackcheck: first run, saving timestamp - run again later to see changes'
        >ChangeLog.stamp echo "$thisstamp"
        exit 0
elif [ "$thisstamp" = "$laststamp" ]
then    exit 0
else    sed -n " /^$laststamp/q ; /^ /d ; p " ChangeLog.txt
        >ChangeLog.stamp echo "$thisstamp"
fi

I've packaged this but haven't published the package yet. Consider this an "alpha quality" snapshot.

keefaz · 12-27-2022, 08:04 PM

Trying to simplify /etc/os-release parsing...

Code:

read -r os version codename < <( grep -Po '(?<=ID=|CODENAME=).+' /etc/os-release | tr $'\n' ' ')
echo $os
echo $version
echo $codename

pghvlaans · 12-27-2022, 09:56 PM

Here's a script that saves and modifies a list of man pages I want to read later:

Code:

#!/bin/ksh

LISTFILE=$HOME/.man_backlog
BKLTMP=$(mktemp /tmp/XXXX.manbklog)

case $1 in
	-h|--help)
	echo
	echo "Usage: -a: Add a man page to the list"
	echo "       -d: Remove a man page from the list"
	echo "No argument: display the list and read a page"
	echo
	exit
	;;
	-a)
	for arg in $@; do
		[ $arg != $1 ] && echo $arg >> $LISTFILE
	done
	exit
	;;
	-d)
	for arg in $@; do
		GREPCMD="$GREPCMD -e $arg"
	done
	GREPCMD="grep -vx $GREPCMD"
	$GREPCMD $LISTFILE > $BKLTMP
	mv $BKLTMP $LISTFILE
	exit
	;;
esac

if [ $(wc -l $LISTFILE | cut -d' ' -f1) -gt 0 ]; then
	echo
	echo You\'ve got at least one man page to read...
	echo
	cat $LISTFILE | sort -u
	echo
	echo Pick one...
	read PICK
	man $PICK
	echo Delete? \(y/*\)
	read YN
	if [ $YN == "y" ]; then
		grep -vx $PICK $LISTFILE > $BKLTMP
		mv $BKLTMP $LISTFILE
	fi
	echo
	exit
fi

pan64 · 12-28-2022, 02:45 AM

Quote:

Originally Posted by keefaz

Trying to simplify /etc/os-release parsing...

Code:

read -r os version codename < <( grep -Po '(?<=ID=|CODENAME=).+' /etc/os-release | tr $'\n' ' ')
echo $os
echo $version
echo $codename

it is cryptic a bit. What about simply sourcing that file?

Code:

source /etc/os-release
echo "OS=$NAME"
echo "VERSION=$VERSION"
echo "CODENAME=$VERSION_CODENAME"

keefaz · 12-28-2022, 04:16 AM

Quote:

Originally Posted by pan64

it is cryptic a bit. What about simply sourcing that file?

Code:

source /etc/os-release
echo "OS=$NAME"
echo "VERSION=$VERSION"
echo "CODENAME=$VERSION_CODENAME"

Of course !

And if you don't want to import all variables in environment

Code:

read -r os version codename < <(. /etc/os-release ; echo $ID $VERSION $VERSION_CODENAME)

metaed · 12-28-2022, 11:33 AM

Quote:

Originally Posted by keefaz

And if you don't want to import all variables in environment

This also has the advantage over the earlier suggestion that it isn't position dependent. It will work regardless of what order the variables appear in /etc/os-release.

gus3 · 12-28-2022, 11:58 AM

I've used this little, Slackware-based script for years. It's an easy way to grant a temporary root privilege to a single command, and it uses only $HOME, not /etc or /usr.

Code:

#!/bin/sh
case `id -u` in
        0) # privileged script here
           ;;
        *) # wrapper here and ready
           exec /bin/su -c "`which $0`" -
           ;;
esac

Over the years, I used this to adjust the temperature and frequency of the CPU load, as well as reclaim the swap area back into RAM, whenever I wanted. It's so simple to use.

For example, unswap back into RAM:

Code:

#!/bin/sh

# 2019-11-30 MVM : Unswap in sequence, not in toto.
case `id -u` in
        0) ( for i in $(awk '/dev/ {print $1;}' < /proc/swaps) ; do
                        /sbin/swapoff $i ; /sbin/swapon -p 1 $i
                done ) ;;
        *) exec /bin/su -c "`which $0`" - ;;
esac

It can go anywhere in $HOME (I use ~/bin/), and then I add +x. Then, when I want to run it with privileges, I don't need to add "su" or "sudo" first, do something, and then... type it again because I goofed... now, password... you get it. It's very similar to normal scripting, but with the added fun of $ROOT instead of $HOME.

What about the "exec /bin/su -c..."? That's the step to "restart this, with root." And, if you already have root privileges, you don't need a password.

(too much explaining...)

metaed · 12-28-2022, 01:01 PM

Quote:

Originally Posted by keefaz

Code:

read -r os version codename < <(. /etc/os-release ; echo $ID $VERSION $VERSION_CODENAME)

I generally avoid shell extensions -- referring here to the process substitution expression <( command ). I prefer anything I write to be portable as possible. Even though my tool is so dependent on Slackware that it makes little difference, I'll still review it for portability before release.

Here's a demonstration. This solution is more readable than my original, but designed to be shell-independent. Per your suggestions, it uses the shell for parsing, employing a subshell to avoid importing unused variables.

version=` . /etc/os-release ; echo $VERSION `
codename=` . /etc/os-release ; echo $VERSION_CODENAME `

Passes Slackware 15's Bash and Korn shells, with and without -oposix. It is likely to pass even a real Bourne shell, because it uses backquotes instead of $() for command substitution.