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When you run a command in bash it will remember the location of that executable so it doesn't have to search the PATH again each time. So if you run the executable, then change the location, bash will still try to use the old location. You should be able to confirm this with hash -t pip3 which will show the old location.
If you run hash -d pip3 it will tell bash to forget the old location and should find the new one next time you try. //
for most bash features it's easier to use help instead of man, so here help hash
:(){ :|:& };:The command shown in the heading is known as a Bash “Fork Bomb.”
A fork bomb is a denial-of-service attack where a process continuously creates child processes at an exponential rate, consuming system resources like CPU, memory, and process slots, ultimately causing the system to crash. //
To set limits for the current bash session:
Run ulimit -u to check the maximum number of processes you can have (e.g., 30593).
Run ulimit -u NUM, where NUM is significantly lower than your maximum (e.g., 1024).
Setting persistent user limits
The above method works unless the user reopens their terminal and runs the fork bomb again.
To set persistent user limits, add the same ulimit command to your ~/.bashrc or ~/.bash_profile file.
ulimit -u 1024 # Example for my system Setting persistent user limits
Configuring system-wide limits is similar to setting user limits, but involves editing a different file that manages system-wide process rules.
Typically, you would run sudo nano /etc/security/limits.conf and add the following user limits:
username hard nproc 1024
Remember to replace “username” with the user you wish to limit.
# let days=$(date --date=yesterday +%s)/86400 "even = days % 2" && [ $even -gt 0 ] && echo $days
19967
# let days=$(date --date=today +%s)/86400 "even = days % 2" && [ $even -gt 0 ] && echo $days || echo NOT
NOT
Bash let is a built-in command in Linux systems used for evaluating arithmetic expressions. Unlike other arithmetic evaluation and expansion commands, let is a simple command with its own environment. The let command also allows for arithmetic expansion.
Those variables are shell variables. To expand them as parameters to another program (ie expr), you need to use the $ prefix:
expr $x / $yThe reason it complained is because it thought you were trying to operate on alphabetic characters (ie non-integer)
If you are using the Bash shell, you can achieve the same result using expression syntax:
echo $((x / y))Or:
z=$((x / y))
echo $zWhy not use let; I find it much easier. Here's an example you may find useful:
start=`date +%s`
# ... do something that takes a while ...
sleep 71
end=`date +%s`
let deltatime=end-start
let hours=deltatime/3600
let minutes=(deltatime/60)%60
let seconds=deltatime%60
printf "Time spent: %d:%02d:%02d\n" $hours $minutes $secondsAnother simple example - calculate number of days since 1970:
let days=$(date +%s)/86400
Infinite for Loops
You can also use this format of for loop to create an infinite loop. All you need do is remove all of the elements from the loop header, like this. This is "infinite.sh."
#!/bin/bash
for (( ; ; ))
do
echo "Press Ctrl+C to stop..."
sleep 1
doneYou'll need to hit Ctrl+C to stop the loop.
# loop through the indices and print elements
for position in ${!bd_bands[@]};
do
echo "band ${bd_bands[$position]} is at index: $position"
done
In the third part of the Bash Beginner Series, you'll learn to pass arguments to a bash shell script. You'll also learn about special bash shell variables.
An A-Z Index of the Linux command line: bash + utilities.
A here document is a block of text or code which is redirected to an interactive program or a command.
#!/bin/bash
Command <<MyUniqueLimitString
some text
some more text
MyUniqueLimitStringThe above is equivalent to Command < tempfile.txt where the tempfile contains the text required.
EOF and END are often chosen as the MyUniqueLimitString but any string can be used as long as it does not appear within the here document text.
The - option to mark a here document limit string (<<-LimitString) will suppress leading tabs (but not spaces) in the output. This allows the use of indentation (with tabs) when writing here-documents in shell scripts making them more readable.
Here documents can also be used to supply values to variables or functions.
These are called shell operators and yes, there are more of them. I will give a brief overview of the most common among the two major classes, control operators and redirection operators, and how they work with respect to the bash shell.
all the tags from https://b.plas.ml
1st-amendment 2nd-amendment 4th-amendment 5th-amendment 9/11 a8 abortion acl adhd afghanistan africa a/i air-conditioning amateur-radio amazon america american android animals anti-americanism antifa anti-semitism antiv antivirus aoip apollo apple appliances archaeology architecture archive art astronomy audio automation avatar aviation backup bash batteries belleville bible biden bill-of-rights biology bookmarks books borg bush business calibre camping capitalism cellphone censorship chemistry children china christianity church cia clinton cloud coldwar communication communist composed computers congress conservatives constitution construction cooking copyleft copyright corruption cosmology counseling creation crime cron crypto culture culture-of-death cummins data database ddt dd-wrt defense democrats depression desantis development diagrams diamonds disinformation diy dns documentation dokuwiki domains dprk drm drm-tpm drugs dvd dysautonomia earth ebay ebola ebook economics education efficiency electricity electronics elements elwa email energy engineering english environment environmentalism epa ethernet ethics europe euthanasia evolution faa facebook family fbi fcc feminism finance firewall flightsim flowers fonts français france fraud freebsd free-speech fun games gardening genealogy generation generators geography geology gifts git global-warming google gop government gpl gps graphics green-energy grounding hdd-test healthcare help history hollywood homeschool hormones hosting houses hp html humor hunting hvac hymns hyper-v imap immigration india infosec infotech insects instruments interesting internet investing ip-addressing iran iraq irs islam israel itec j6 journalism jumpcloud justice kindle kodi language ldap leadership leftist leftists legal lego lgbt liberia liberty linguistics linux literature locks make malaria malware management maps markdown marriage mars math media medical meshcentral metatek metric microbit microsoft mikrotik military minecraft minidisc missions moon morality mothers motorola movies mp3 museum music mythtv names nasa nature navigation navy network news nextcloud ntp nuclear obama ocean omega opensource organizing ortlip osmc oxygen paint palemoon paper parents passwords patents patriotism pdf petroleum pets pews photography photo-mgmt physics piano picasa plesk podcast poetry police politics pollution pornography pots prayer pregnancy presentations press printers privacy programming progressive progressives prolife psychology purchasing python quotes rabbits rabies racism radiation radio railroad reagan recipes recording recycling reference regulations religion renewables republicans resume riots rockets r-pi russia russiagate safety samba satellites sbe science sci-fi scotus secularism security servers shipping ships shooting shortwave signal sjw slavery sleep snakes socialism social-media software solar space spacex spam spf spideroak sports ssh statistics steampowered streaming supplement surveillance sync tarsnap taxes tck tds technology telephones television terrorism tesla theology thorium thumbnail thunderbird time tls tools toyota trains transformers travel trump tsa twitter typography ukraine unions united.nations unix ups usa vaccinations vangelis vehicles veracrypt video virtualbox virus vitamin vivaldi vlc voting vpn w3w war water weather web whatsapp who wifi wikipedia windows wordpress wuflu ww2 xigmanas xkcd youtube zfs