Shell Programming and Scripting

# further process sorted find list by checking each file pair with cmp
while read input
do
#  remove leading . from each line in find output
   TEMP=$(echo $input | sed 's/^.//g')
#  escape spaces
   LOCALFILE=$(echo $TEMP | sed 's/ /\\ /g')

   echo $TREE1$LOCALFILE
   echo $TREE2$LOCALFILE

   cmp $TREE1$LOCALFILE  $TREE2$LOCALFILE > $TMPDIR'/byte_compare.txt'

done < $TMPDIR'/check_1_sorted'

SIZE1=$(stat -c%s "$TREE1$LOCALFILE")
SIZE2=$(stat -c%s "$TREE2$LOCALFILE")

if [ "$SIZE1" != "$SIZE2" ]; then
   echo "$TREE1$LOCALFILE" >> $TMPDIR'/size_compare.txt'
fi

#!/usr/bin/env bash

# @(#) s1	Demonstrate compare timings for stat and cmp.

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
# export PATH="/usr/local/bin:/usr/bin:/bin"
pe() { for _i;do printf "%s" "$_i";done; printf "\n"; }
pl() { pe;pe "-----" ;pe "$*"; }
db() { ( printf " db, ";for _i;do printf "%s" "$_i";done;printf "\n" ) >&2 ; }
db() { : ; }
C=$HOME/bin/context && [ -f $C ] && $C stat cmp

N=${1-10000}

pl " Input data file f1 f2:"
specimen -3 -n f1 f2 | cut -c1-78

pl " Results, time for $N stat calls:"
rm -f f3
time for ((i=1;i<=$N;i++))
do
  s1=$(stat -c%s f1)
  s2=$(stat -c%s f2)
  if [ "$s1" != "$s2" ]
  then 
    pe "f1" >> f3
  fi
done
if [ -e f3 ]
then
  pe " Lines in f3: $(wc -l <f3)"
fi

pl " Results, time for $N cmp calls:"
rm -f f3
time for ((i=1;i<=$N;i++))
do
  if ! cmp f1 f2
  then
    pe "f1" >> f3
  fi
done
if [ -e f3 ]
then
  pe " Lines in f3: $(wc -l <f3)"
fi

exit 0

./s1

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.26-2-amd64, x86_64
Distribution        : Debian GNU/Linux 5.0.8 (lenny) 
bash GNU bash 3.2.39
stat (GNU coreutils) 6.10
cmp (GNU diffutils) 2.8.1

-----
 Input data file f1 f2:
Edges: 3:0:3 of 17777 lines in file "f1"
     1	Preliminary Matter.  
     2	
     3	This text of Melville's Moby-Dick is based on the Hendricks House editi
   ---
 17775	THEY GLIDED BY AS IF WITH PADLOCKS ON THEIR MOUTHS; THE SAVAGE SEA-HAWK
 17776	D WITH SHEATHED BEAKS. +ON THE SECOND DAY, A SAIL DREW NEAR, NEARER, AN
 17777	KED ME UP AT LAST. +IT WAS THE DEVIOUS-CRUISING +RACHEL, THAT IN HER RE

Edges: 3:0:3 of 17777 lines in file "f2"
     1	Preliminary Matter.  
     2	
     3	This text of Melville's Moby-Dick is based on the Hendricks House editi
   ---
 17775	THEY GLIDED BY AS IF WITH PADLOCKS ON THEIR MOUTHS; THE SAVAGE SEA-HAWK
 17776	D WITH SHEATHED BEAKS. +ON THE SECOND DAY, A SAIL DREW NEAR, NEARER, AN
 17777	KED ME UP AT LAST. +IT WAS THE DEVIOUS-CRUISING +RACHEL, THAT IN HER RE

-----
 Results, time for 10000 stat calls:

real	0m39.595s
user	0m10.397s
sys	0m27.694s

-----
 Results, time for 10000 cmp calls:

real	0m55.188s
user	0m27.122s
sys	0m25.958s

#!/usr/bin/env perl

# @(#) p1	Demonstrate stat on open (and un-opened) files.

use strict;
use warnings;

my ($debug);
$debug = 1;
$debug = 0;

my ( $f1, $f2, $f3 );
my ( $s1, $s2, $i, $j, $N );

# Make sure files are around, then close them.
open( $f1, "<", "f1" ) || die " Cannot open file f1\n";
open( $f2, "<", "f2" ) || die " Cannot open file f2\n";
open( $f3, ">", "f3" ) || die " Cannot open file f3 for write\n";
$s1 = ( stat("f1") )[7];
$s2 = ( stat("f2") )[7];
print " Length of f1, f2: $s1, $s2\n";
close $f1;
close $f2;

$j = 0;
$N = 10;
$N = 10000;
for ( $i = 1; $i <= $N; $i++ ) {
  $s1 = rand();
  $s2 = rand();
  $s1 = ( stat("f1") )[7];
  $s2 = ( stat("f2") )[7];
  if ( $s1 != $s2 ) {
    print $f3 " Found mismatch at iteration $i\n";
    $j++;
  }
  print " Length of f1, f2: $s1, $s2\n" if $debug;
}
print STDERR " Called stat $i (-1) times on each file, compared sizes.\n";
if ( $j != 0 ) {
  print STDERR " File f3 was written to $j times.\n";
}

exit(0);

time ./p1
 Length of f1, f2: 1205404, 1205404
 Called stat 10001 (-1) times on each file, compared sizes.

real	0m0.091s
user	0m0.036s
sys	0m0.040s