bashoneliners.com

Welcome to bashoneliners.com, a growing collection of practical and well-explained Bash one-liners, snippets, tips and tricks. We review and improve every contributed one-liner to make sure it is of high quality: useful, easy to read, follows best practices, with clear, detailed, accurate explanation. These one-liners should help you automate tasks, troubleshoot problems, whether it be in system administration, file management, networking or programming.

0

The robust way to read lines in a loop

while IFS= read -r line || [[ $line ]]; do ...; done < /path/to/input

September 28, 2023bashoneliners

0

Watch a mashup of many video files

L=5; while true; do; readarray -t paths < <(find . -type f -print | shuf -n 1); for i in "${!paths[@]}"; do; path=${paths[i]}; if ffprobe -i "$path" -show_entries format=duration -v quiet -of csv="p=0" > /dev/null; then; N=$(ffprobe -i "$path" -show_entries format=duration -v quiet -of csv="p=0"); D=${N%.*}; P=$((D / 100 * 25)); R=$((1 + RANDOM % D - P * 2)); S=$((P + RANDOM % R)); W=$((R / 4)); LEN=$((1 + RANDOM % L)); mpv "$path" --start="$S" --length="$LEN" --fs &> /dev/null; W=$(bc <<< "$LEN - 0.5"); sleep "$W"; unset 'paths[i]'; fi; done; done

July 6, 2023krypniok

1

Unzip logrotated files in order and print concatenated content

(cd /var/log && ls syslog* | sort -n -t. -k2 | while read file; do echo "===== $file ====="; zcat "$file" || cat "$file"; done)

June 16, 2023harisokanovic

0

While loop to pretty print system load (1, 5 & 15 minutes)

while :; do date; awk '{printf "1 minute load: %.2f\n", $1; printf "5 minute load: %.2f\n", $2; printf "15 minute load: %.2f\n", $3}' /proc/loadavg; sleep 3; done

September 5, 2018bashoneliners

0

While loop to pretty print system load (1, 5 & 15 minutes)

while [ 1 == 1 ]; do  cat /proc/loadavg | awk '{printf "1 minute load: %.2f\n", $(NF-5)}' && cat /proc/loadavg |awk '{printf "5 minute load: %.2f\n", $(NF-3)}' && cat /proc/loadavg |awk '{printf "15 minute load: %.2f\n", $(NF-2)}'; sleep 3; date; done

August 30, 2018peek2much3

1

Have script run itself in a virtual terminal

tty >/dev/null || { urxvt -e /bin/sh -c "tty >/tmp/proc$$; while test x; do sleep 1; done" & while test ! -f /tmp/proc$$; do sleep .1; done; FN=$(cat /tmp/proc$$); rm /tmp/proc$$; exec >$FN 2>$FN <$FN; }

March 9, 2018openiduser111

1

Delete orphan vi and vim undo files

find . -type f -iname '*.un~' | while read UNDOFILE ; do FILE=$( echo "$UNDOFILE" | sed -r -e 's/.un~$//' -e 's&/\.([^/]*)&/\1&' ) ; [[ -e "$FILE" ]] || rm "$UNDOFILE" ; done

September 2, 2014rafaeln

7

Display the number of connections per IP to port 80

while true; do clear; date; echo; echo "[Count] | [IP ADDR]"; echo "-------------------"; netstat -n | grep ':80\>' | awk '! /LISTEN/ {print $5}' | cut -d: -f1 | uniq -c; sleep 5; done

April 9, 2014cesp

1

Define an own watch(1)-like function

watch () { interrupted=false; trap "interrupted=true" INT; while ! $interrupted; do $*; sleep 1 || interrupted=true; done; }

November 14, 2012ulidtko

1

Calculate an h index from an EndNote export

MAX=$(NUM=1;cat author.xml |perl -p -e 's/(Times Cited)/\n$1/g'|grep "Times Cited" |perl -p -e 's/^Times Cited:([0-9]*).*$/$1/g'|sort -nr | while read LINE; do if [ $LINE -ge $NUM ]; then echo "$NUM"; fi; NUM=$[$NUM+1]; done;); echo "$MAX"|tail -1

February 4, 2012openiduser14

1

Group count sort a log file

A=$(FILE=/var/log/myfile.log; cat $FILE | perl -p -e 's/.*,([A-Z]+)[\:\+].*/$1/g' | sort -u | while read LINE; do grep "$LINE" $FILE | wc -l | perl -p -e 's/[^0-9]+//g'; echo -e "\t$LINE"; done;);echo "$A"|sort -nr

January 31, 2012openiduser14

0

Delete all tables of a mysql database

mysql --defaults-file=my.cnf -e 'show tables' | while read t; do mysql --defaults-file=my.cnt  -e 'drop table '$t; done

January 8, 2012bashoneliners

0

Remove all the versioned-but-empty directories from a Subversion checkout

find . -name .svn -type d | while read ss; do dir=$(dirname "$ss"); test $(ls -a "$dir" | wc -l) == 3 && echo "svn rm \"$dir\""; done

November 27, 2011bashoneliners

0

Alert me by email when a disconnected or unreachable server comes back online

while ! ping -c1 the_host_down; do sleep 1; done && date | mail -s 'the host is back!' me@example.com

October 10, 2011janos

0

Add timestamp to the output of ping

ping some_host | while read LINE; do echo $(date): $LINE; done

October 10, 2011janos

0

Test a one-liner with echo commands first, pipe to bash when ready

paste <(ls) <(ls | tr A-Z a-z) | while read OLD NEW; do echo mv -v $OLD $NEW; done | sh

October 8, 2011janos

2

Remove spaces recursively from all subdirectories of a directory

find /path/to/dir -type d | tac | while read LINE; do target=$(dirname "$LINE")/$(basename "$LINE" | tr -d ' '); echo mv "$LINE" "$target"; done

September 20, 2011bashoneliners

2

Rename all files in a directory to lowercase names

paste <(ls) <(ls | tr A-Z a-z) | while read OLD NEW; do echo mv -v $OLD $NEW; done

August 5, 2011bashoneliners