Shell Programming and Scripting

#!/usr/bin/env bash

# @(#) s4       Demonstrate gathering, perfect shuffle, with paste.

echo
set +o nounset
LC_ALL=C ; LANG=C ; export LC_ALL LANG
echo "Environment: LC_ALL = $LC_ALL, LANG = $LANG"
echo "(Versions displayed with local utility \"version\")"
version >/dev/null 2>&1 && version "=o" $(_eat $0 $1) paste jot
set -o nounset
echo

FILE1=data1
FILE2=data2

echo
echo " Data file $FILE1:"
cat $FILE1

echo
echo " Data file $FILE2:"
cat $FILE2

echo
echo " Results:"
n=$( wc -l $FILE1 )
paste -d '\n' $FILE1 $FILE2 <( jot -b "===" $n )

exit 0

% ./s4

Environment: LC_ALL = C, LANG = C
(Versions displayed with local utility "version")
OS, ker|rel, machine: Linux, 2.6.11-x1, i686
Distribution        : Xandros Desktop 3.0.3 Business
GNU bash 2.05b.0
paste (coreutils) 5.2.1
jot - ( /usr/bin/jot Aug 18 2003 )


 Data file data1:
Aaa
Bbb
Ccc
Ddd
Eee
Fff

 Data file data2:
Zzz
Yyy
Xxx
www
vvv
uuu

 Results:
Aaa
Zzz
===
Bbb
Yyy
===
Ccc
Xxx
===
Ddd
www
===
Eee
vvv
===
Fff
uuu
===

 $ cat test.py
#!/usr/bin/env python

file1 = open('f1', 'r')
file2 = open('f2', 'r')

for line in file1:
    print line,
    print file2.readline(),
    print "--"

paste -d"\n" file1 file2 | awk '{print;if(NR%2==0){print "----"}}'

#!/bin/sh
 exec 3< file1.txt    # Open file1.txt for input on file descriptor 3
 exec 4< file2.txt    # Open file2.txt for input on file descriptor 4
 
 while : ; do    
     read <&3 line1        # read next line from file1.txt into line1
     [ $? -ne 0 ] && break # If finished reading file1, break out of loop.
     echo "$line1"         # otherwise print the line.
     read <&4 line2        # do the same for file2.txt
     echo "$line2"
     echo "-----"  
 done
 
 3<&-    # Close the file descriptors
 4<&-

#!/bin/sh
exec 3< file1.txt    # Open file1.txt for input on file descriptor 3
exec 4< file2.txt    # Open file2.txt for input on file descriptor 4
F1=0 F2=0            # Flags indicating file has more to read, 0 = true in shell.

while [ $F1 -eq 0 -o $F2 -eq 0 ]; do    # At least one file has more to read
   read <&3 line1        # read file1
   F1=$?                 # Gets set to non-zero if finished reading
   [ $F1 -eq 0 ] && echo "$line1"   # don't print if we didn't read something.
   
   read <&4 line2
   F2=$?
   [ $F2 -eq 0 ] && echo "$line2"
    
   [ $F1 -eq 0 -a $F2 -eq 0 ] && echo "-----"   # Print if both files are still reading

done

3<&-    # Close the file descriptors
4<&-