UNIX for Advanced & Expert Users

#!/usr/bin/env bash

# @(#) s1	Demonstrate cat copying a system executable file.

# Utility functions: print-as-echo, print-line-with-visual-space, debug.
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 cat

# Remove debris, list current situation..
pl " Current situation:"
rm -f f1
/bin/ls -lgG

# Copy executable with cat, look at type, make it executable.
pl " New file characteristics:"
cat /bin/ls > f1
file f1
chmod +x f1

# Run it.
pl " Results of executing copy of file:"
./f1 -lgG

# Compare the files with cmp.
pl " Results of comparison:"
if cmp --quiet /bin/ls f1
then
  pe " Files are the same according to cmp."
else
  pe " Files differ."
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 5.0.7 (lenny) 
GNU bash 3.2.39
cat (GNU coreutils) 6.10

-----
 Current situation:
total 4
-rwxr--r-- 1 836 Mar 28 16:44 s1

-----
 New file characteristics:
f1: ELF 64-bit LSB executable, x86-64, version 1 (SYSV), dynamically linked (uses shared libs), for GNU/Linux 2.6.8, stripped

-----
 Results of executing copy of file:
total 108
-rwxr-xr-x 1 101992 Mar 28 16:45 f1
-rwxr--r-- 1    836 Mar 28 16:44 s1

-----
 Results of comparison:
 Files are the same according to cmp.