To sort “ls” by date use:
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ls -lt |
To make it more friendly use:
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ls -halt |
Archive | Bash Scripting
Loop over lines in shell pipeline
To loop over a list of line do this:
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ls -al | while IFS= read -r line ; do echo $line; done |
Convert newlines to spaces
TR can be used to convert a list of items from one per line to space separated with this:
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tr '\r\n' ' ' |
Get IP Address In A Script
Recently needed a good way to fetch the IP address of each interface within a script. Tried things like:
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ifconfig | grep 'inet addr:'| grep -v '127.0.0.1' | cut -d: -f2 | awk '{ print $1}' |
and
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/sbin/ifconfig | sed -n '2 p' | awk '{print $3}' |
But this is fairly ugly. So I tried:
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hostname -I |
This gives a list of IP addresses but they are un-ordered so I can’t guarantee which address goes with which interface. Here’s one using “ip addr”:
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ip=$(ip -f inet -o addr show eth0|cut -d\ -f 7 | cut -d/ -f 1) |
Still very messy. Finally, found the “ifdata” command which is part of the “moreutils” package. First make sure “moreutils” is installed with:
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yum -y install moreutils |
Now you can query for a wide range of different information:
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Usage: ifdata [options] iface -e Reports interface existence via return code -p Print out the whole config of iface -pe Print out yes or no according to existence -pa Print out the address -pn Print netmask -pN Print network address -pb Print broadcast -pm Print mtu -ph Print out the hardware address -pf Print flags -si Print all statistics on input -sip Print # of in packets -sib Print # of in bytes -sie Print # of in errors -sid Print # of in drops -sif Print # of in fifo overruns -sic Print # of in compress -sim Print # of in multicast -so Print all statistics on output -sop Print # of out packets -sob Print # of out bytes -soe Print # of out errors -sod Print # of out drops -sof Print # of out fifo overruns -sox Print # of out collisions -soc Print # of out carrier loss -som Print # of out multicast -bips Print # of incoming bytes per second -bops Print # of outgoing bytes per second |
So here are some examples:
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[root@host]# ifdata -pa eth0 10.210.160.53 [root@host]# ifdata -pa eth0 10.210.160.53 [root@host]# ifdata -pn eth0 255.255.224.0 [root@host]# ifdata -sip eth0 1622384587 [root@host]# ifdata -bops eth0 896 |
Overall this is much cleaner and more reliable then the earlier approaches.
maxclients.sh Script For Apache
This script attempts to look at Apache memory usage and recommend a stable setting for MaxClients.
Shell
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#!/bin/bash PROCNAME=httpd PARENTPIDS=`comm -12 <(ps -C $PROCNAME -o ppid | sort -u) <(ps -C $PROCNAME -o pid | sort -u)` for ParPID in $PARENTPIDS; do SUM=0 COUNT=0 for x in `ps f --ppid $ParPID -o rss | tail -n +2`; do SUM=$(( $SUM + $x )) COUNT=$(( $COUNT + 1 )) done MEMPP=$(( $SUM / $COUNT / 1024 )) FREERAM=$(( `free | tail -2 | head -1 | awk '{print $4}'` / 1024 )) APACHERAM=$(( $SUM / 1024 )) APACHEMAX=$(( $APACHERAM + $FREERAM )) ( echo echo "Info for the following parent apache process:" echo " "`ps f --pid $ParPID -o command | tail -n +2` echo echo "Current # of apache processes: $COUNT" echo "Average memory per apache process: $MEMPP MB" echo "Free RAM (including cache & buffers): $FREERAM MB" echo "RAM currently in use by apache: $APACHERAM MB" echo "Max RAM available to apache: $APACHEMAX MB" echo echo "Theoretical maximum MaxClients: $(( $APACHEMAX / $MEMPP ))" echo "Recommended MaxClients: $(( $APACHEMAX / 10 * 9 / $MEMPP ))" echo ) done |
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