Shell Programming and Scripting

#!/usr/bin/env bash

# @(#) s1	Demonstrate complexity of sed compared to awk.

# Utility functions: print-as-echo, print-line-with-visual-space.
pe() { for i;do printf "%s" "$i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }

FILE=${1-data1}

pl " Input file $FILE:"
cat $FILE

pl " Results, sed:"
sed -n '/^Mem:/s/^[^0-9]*\([0-9]*.\).*$/\1/p' $FILE

exit 0

% ./s1

-----
 Input file data1:
top - 09:45:10 up 15:48,  1 user,  load average: 0.07, 0.02, 0.00
Tasks: 112 total,   1 running, 111 sleeping,   0 stopped,   0 zombie
Cpu(s):  0.0%us,  0.0%sy,  0.0%ni,100.0%id,  0.0%wa,  0.0%hi,  0.0%si,  0.0%st
Mem:   1025740k total,  1012624k used,    13116k free,   428188k buffers
Swap:  3004112k total,    74580k used,  2929532k free,   134616k cached

  PID USER      PR  NI  VIRT  RES  SHR S %CPU %MEM    TIME+  COMMAND
    1 root      20   0  2848 1688  544 S    0  0.2   0:02.12 init
    2 root      15  -5     0    0    0 S    0  0.0   0:00.00 kthreadd

-----
 Results, sed:
1025740k

top |  sed -n '/^Mem:/s/^[^0-9]*\([0-9]*.\).*$/\1/p'

top | awk '/Mem/{print "Mem: " $2}'

top -b -n1 | sed -n '/Mem/s/ [a-z]\+.*//p'