Stupid Shell Tricks
Shell invocation
/bin/sh
-u - treat the use of unset variables as errors. -x - show me execution.
PS for swap
ps -eo pcpu,pid,pmem,rss,vsz,comm --sort=-rss
PS1
export PS1='[\u@\h \t \w]\$ '
Command line Tools
Diff
alias diffss='diff --width=180 --suppress-common-lines --side-by-side'
pwgen
pwgen -B -c -n -y
- unabiguous
- 1 capital
- 1 number
- 1 special char
Printing /proc/<pid>/environ
cat /proc/<pid>/environ | xargs --null --max-args=1 echo
cat /proc/(pidof process)/environ | tr '\0' '^M'
cat /proc/(pidof process)/environ | tr '\0' '<control-v><enter>'
HTTP response codes - filter
tail -f /var/log/httpd/access | awk '$9 !=200'
the print is implied, $9 happens to be where the http response code is in my log: 200 means OK, so it's show me the NOT OK stuff.
Disk usage report
du -x --max-depth=1 / | sort -rn
Date
shell var of NOW
NOW=`date +%a.%d.%b.%Y`
result:
Mon.04.Jul.2016
for DNS serial numbers:
NOW=`date "+%Y%m%d%H%M%S"`
result:
20160704174515
iso styleee!
$ date --iso-8601=seconds 2017-06-06T11:14:05-0400
Javascript
date "+%Y-%m-%dT%H:%M:%S.000Z"
some unix dates can't do millis, so just set to 000
shell var for shadowLastChange (ldap)
echo $((`date --utc --date "$1" +%s`/86400))
Days since the UNIX epoch
Return the number of days since the UNIX epoch using perl:
perl -e 'printf qq{%d\n},time/86400'
Convert /etc/shadow lastchg to date
Convert the lastchg field in /etc/shadow to a date using GNU date:
date -d "1 January 1970 + lastchg days"
Set timezone
set it system wide:
sudo timedatectl set-timezone Europe/Brussels
for your shell
export TZ=timezone
Links
fake_tomcat.sh
ARGV="$@" if [ "x$ARGV" = "x" ] ; then echo usage: all start, stop, reload, abort, flush, or check exit fi case $# in 0) echo 'Usage: ./snapshot <CPE name> (ie, ./snapshot YCDECUBC)' 1>&2; exit 2 esac trap 'echo "";exit 3' 2 15 trap 'echo fake_tomcat.sh caught 1 HUP \-\> ok bye\! ; exit 3' 1 trap 'echo fake_tomcat.sh caught 3 QUIT \-\> ok bye\! ; exit 3' 3 trap 'echo fake_tomcat.sh caught 9 KILL \-\> ok bye\! ; exit 3' 9 trap 'echo fake_tomcat.sh caught 15 TERM \-\> ok bye\! ; exit 3' 15 TMPFILE=`mktemp /tmp/$0.XXXXXX` || exit 1 To move/duplicate filesystems I have a favorite way to do it locally: # cd $filesystem_to_duplicate # find . -print | cpio -pvdm /mnt ...where /mnt is the new filesystem/slice. To duplicate/move across the network do it like this: # cd $filesystem_to_duplicate # tar cf - . | ssh otherhost "cd /$new_filesystem ; tar xf -" function waitfor { if [ $# -lt 1 ] ; then echo "nothing to wait for" else echo "ok I'll wait" echo Still running = 1 STILL_RUNNING=1 while [ $STILL_RUNNING -gt 0 ] do STILL_RUNNING=`ps -auwwwx | grep $1 | grep -v grep | wc -l` echo STILL_RUNNING = $STILL_RUNNING sleep 1 echo waiting... done fi echo $1 } | tr '\n' ',' TimerOn() { sleep $TIMELIMIT && kill -s 14 $$ & # Waits 3 seconds, then sends sigalarm to script. } Int14Vector() { answer="TIMEOUT" PrintAnswer exit 14 } trap Int14Vector 14
While loops for Fun and Profit
this script runs until you stop it. It collects file handle usage on a server putting the results in a file in the form:
<timestamp> <total allocated> <free> <maxpossible>
the last three field are from the /proc fs:
3391 969 52427 | | | | | | | | maximum open file descriptors | total free allocated file descriptors total allocated file descriptors (the number of file descriptors allocated since boot)
scripts:
while true; do echo `date +%s` | awk 'BEGIN{ORS=""}{print $0 " "}' >> /home/dathornton/s4.t55.file-nr.2008040300; cat /proc/sys/fs/file-nr >> /home/dathornton/s4.t55.file-nr.2008040300; sleep 5; done
You MUST MUST MUST put the sleep in there or "Bad Things Will Happen"(tm), it will loop too fast and you device could crash.
or in one line:
while true; do echo `date +%s` | awk 'BEGIN{ORS=""}{print $0 " "}' >> /home/dathornton/servername.file-nr.2008040300; cat /proc/sys/fs/file-nr >> /home/dathornton/servername.file-nr.2008040300; sleep 5; done
while loop over multi column input
tl;dr:
k get cm -A | grep ggr | awk '{print $1 , $2}' | while read ns cm; do echo ns is $ns; echo cm is $cm ; done <&0
You are looking for something in a kubernetes configmap ( cm ). You query all configmaps for all names spaces
k get cm -A
and grep out a term. You don't want all those columns, you want the first two: namespace and configmap name.
grep ggr | awk '{print $1 , $2}'
now comes the fun part, you do while loop with a read, and by sending it &0 ( the stdin file descriptor ) , you can read the pipe you were given.
while read ns cm; do echo ns is $ns; echo cm is $cm ; done <&0
until loops
until PGPASSWORD=$POSTGRES_PASSWORD psql -h "$host" -U "postgres" -c '\q'; do >&2 echo "Postgres is unavailable - sleeping" sleep 1 done
Traps
#!/bin/bash # traptest.sh trap "echo Booh!" SIGINT SIGTERM trap "echo Kill" SIGKILL echo "pid is $$" while: # This is the same as "while true". do sleep 5 # This script is not really doing anything. done
sort
Sorting Hostnames
service<instance>.location<instance>.fart.gas.bum
sort -t . -k2.2,1.1n -k1n
Sorting Ip Addresses
By Last three octets:
sort -t . -k 2,2n -k 3,3n -k 4,4n serverlist| more
epoch
#!/bin/sh date -d "1970-01-01 UTC $1 seconds"
bash
disable bell
echo "set bell-style none" >> ~/.inputrc
timestamps in history
export HISTTIMEFORMAT='%F %T '
Awk
show me lines that don't have that in field 2
awk ' $2 !~ "[A-Za-z]" {print $0}'
who me lines that have less than 2 field:
awk ' NF < 2 {print $0}'
or shorter:
awk 'NF<2'
gimme field 2 - end (squash the first field then strip the leading space.)
awk '{$1=""; sub(/^space:*/,""); print}'
"Crontab last Saturday of the month" problem
- Client had a problem where they wanted a script run on a server at 11 pm on the last Saturday of the month
- the crontab that was originally devised was:
#0 11 1-6 * 6 /home/smsadmin/CPU_util/runall.sh *snip*
- this ended up running at 11am from the 1st of the month to the 6th of the month, *as well as* every Saturday, NOT on Saturday as long as it was only the 1st to the 6th (this is somewhat unintuitive).
- to work around this, we wrote a quick wrapper 1-liner script that returned true if the same day next week had a different month than this month:
0 11 * * 6 [ $(date +\%m) != $(date +\%m -d "next week") ] && <rest of the command to run if the test passed>
find
find recent large stuff on /
find / -xdev -mtime -1 -size +10M | xargs ls -lad
Which process is on which cpu?
ps -eo psr,pid,tid,nlwp,tty,comm
or sorted by processor:
ps -eo psr,pid,tid,nlwp,tty,comm | sort -n
ps doesn't seem to want to sort on processor. These don't work:
ps --sort=psr -eo psr,pid,tid,nlwp,tty,comm ps --sort psr -eo psr,pid,tid,nlwp,tty,comm ps kpsr -eo psr,pid,tid,nlwp,tty,comm
how many processes on which cpu?
ps h -eo psr | sort | uniq -c | awk '{printf "%4s %4s\n", $2 ,$1}' | sort -n
Sed
grep out one variable with sed
cat /var/log/zimbra.log | sed -n 's/.*client=//p' | sort |uniq -c|sort -rn | head -30
remove terminal colours
sed 's/\x1b\[[0-9;]*m//g'
set / unset / empty
+----------------------+------------+-----------------------+-----------------------+ | if VARIABLE is: | set | empty | unset | +----------------------+------------+-----------------------+-----------------------+ - | ${VARIABLE-default} | $VARIABLE | "" | "default" | = | ${VARIABLE=default} | $VARIABLE | "" | $(VARIABLE="default") | ? | ${VARIABLE?default} | $VARIABLE | "" | exit 127 | + | ${VARIABLE+default} | "default" | "default" | "" | +----------------------+------------+-----------------------+-----------------------+ :- | ${VARIABLE:-default} | $VARIABLE | "default" | "default" | := | ${VARIABLE:=default} | $VARIABLE | $(VARIABLE="default") | $(VARIABLE="default") | :? | ${VARIABLE:?default} | $VARIABLE | exit 127 | exit 127 | :+ | ${VARIABLE:+default} | "default" | "" | "" | +----------------------+------------+-----------------------+-----------------------+
ref: https://stackoverflow.com/questions/3601515/how-to-check-if-a-variable-is-set-in-bash
parallel processes , ghetto style
{ xargs -P 3 -I {} sh -c 'eval "$1"' - {} <<'EOF' sleep 1; echo 1 sleep 2; echo 2 sleep 3; echo 3 echo 4 EOF } &
intercepting options with bash
Something runs a program, it's hard coded it to run it a certain way, you want to run it a different way, say with different otions.
swap the binary out, and put a small shell script in the way:
in this exmaple the original runs chrome drvier with --port=XX and --log-path=/dev/null.
You want to keep the port, but change the logging.
mv /usr/bin/chromedriver /usr/bin/chromedriver.binary
heredoc user:user 755 /usr/bin/chromedriver <<<
#!/bin/bash re="--port=([0-9]*?) " if [[ $@ =~ $re ]]; then port=${BASH_REMATCH[1]} /usr/bin/chromedriver.binary --port=${port} --log-path=/tmp/chromedriver.log --log-level=INFO --append-log else echo "no port specified" exit 1 fi