SHELL下十二种读文件的方法 [转载]

#!/usr/bin/ksh 
# 
# SCRIPT: 12_ways_to_parse.ksh.ksh 
# 
# 
# REV: 1.2.A 
# 
# PURPOSE:  This script shows the different ways of reading 
#       a file line by line.  Again there is not just one way 
#       to read a file line by line and some are faster than 
#       others and some are more intuitive than others. 
# 
# REV LIST: 
# 
#       03/15/2002 - Randy Michael 
#       Set each of the while loops up as functions and the timing 
#       of each function to see which one is the fastest. 
# 
####################################################################### 
# 
#       NOTE: To output the timing to a file use the following syntax: 
# 
#          12_ways_to_parse.ksh file_to_process  > output_file_name 2>&1 
# 
#       The actaul timing data is sent to standard error, file  
#       descriptor (2), and the function name header is sent 
#       to standard output, file descriptor (1). 
# 
####################################################################### 
# 
# set -n  # Uncomment to check command syntax without any execution 
# set -x  # Uncomment to debug this script 
# 

FILENAME="$1" 
TIMEFILE="/tmp/loopfile.out" 
>$TIMEFILE 
THIS_SCRIPT=$(basename $0) 

###################################### 
function usage 
{ 
echo "\nUSAGE: $THIS_SCRIPT  file_to_process\n" 
echo "OR - To send the output to a file use: " 
echo "\n$THIS_SCRIPT  file_to_process  > output_file_name 2>&1 \n" 
exit 1 
} 
###################################### 
function while_read_LINE 
{ 
cat $FILENAME | while read LINE 
do 
        echo "$LINE" 
        : 
done 
} 
###################################### 
function while_read_LINE_bottom  
{ 
while read LINE 
do 
        echo "$LINE" 
        : 

done < $FILENAME 
} 
###################################### 
function while_line_LINE_bottom 
{ 
while line LINE 
do 
        echo $LINE 
        : 
done < $FILENAME 
} 
###################################### 
function cat_while_LINE_line   
{ 
cat $FILENAME | while LINE=`line` 
do 
        echo "$LINE" 
        : 
done 
} 
###################################### 
function while_line_LINE 
{ 
cat $FILENAME | while line LINE 
do 
        echo "$LINE" 
        : 
done 
} 
###################################### 
function while_LINE_line_bottom  
{ 
while LINE=`line` 
do 
        echo "$LINE" 
        : 

done < $FILENAME  
} 
###################################### 
function while_LINE_line_cmdsub2  
{ 
cat $FILENAME | while LINE=$(line) 
do 
        echo "$LINE" 
        : 
done 
} 
###################################### 
function while_LINE_line_bottom_cmdsub2  
{ 
while LINE=$(line) 
do 
        echo "$LINE" 
        : 

done < $FILENAME  
} 
###################################### 
function while_read_LINE_FD  
{ 
exec 3<&0 
exec 0< $FILENAME 
while read LINE 
do 
        echo "$LINE" 
        : 
done 
exec 0<&3 
} 
###################################### 
function while_LINE_line_FD  
{ 
exec 3<&0 
exec 0< $FILENAME 
while LINE=`line` 
do 
        echo "$LINE" 
        : 
done 
exec 0<&3 
} 
###################################### 
function while_LINE_line_cmdsub2_FD 
{ 
exec 3<&0 
exec 0< $FILENAME 
while LINE=$(line) 
do 
        print "$LINE" 
        : 
done 
exec 0<&3 
} 
###################################### 
function while_line_LINE_FD  
{ 
exec 3<&0 
exec 0< $FILENAME 

while line LINE 
do 
        echo "$LINE" 
        : 
done 

exec 0<&3 
} 
###################################### 
########### START OF MAIN ############ 
###################################### 

# Test the Input 

# Looking for exactly one parameter 
(( $# == 1 )) || usage 

# Does the file exist as a regular file? 
[[ -f $1 ]] || usage 

echo "\nStarting File Processing of each Method\n" 

echo "Method 1:" 
echo "\nfunction while_read_LINE\n" >> $TIMEFILE 
echo "function while_read_LINE" 
time while_read_LINE >> $TIMEFILE 
echo "\nMethod 2:" 
echo "\nfunction while_read_LINE_bottom\n" >> $TIMEFILE 
echo "function while_read_LINE_bottom" 
time while_read_LINE_bottom >> $TIMEFILE 
echo "\nMethod 3:" 
echo "\nfunction while_line_LINE_bottom\n" >> $TIMEFILE 
echo "function while_line_LINE_bottom" 
time while_line_LINE_bottom >> $TIMEFILE 
echo "\nMethod 4:" 
echo "\nfunction cat_while_LINE_line\n" >> $TIMEFILE 
echo "function cat_while_LINE_line" 
time cat_while_LINE_line >> $TIMEFILE 
echo "\nMethod 5:" 
echo "\nfunction while_line_LINE\n" >> $TIMEFILE 
echo "function while_line_LINE" 
time while_line_LINE >> $TIMEFILE 
echo "\nMethod 6:" 
echo "\nfunction while_LINE_line_bottom\n" >> $TIMEFILE 
echo "function while_LINE_line_bottom" 
time while_LINE_line_bottom >> $TIMEFILE 
echo "\nMethod 7:" 
echo "\nfunction while_LINE_line_cmdsub2\n" >> $TIMEFILE 
echo "function while_LINE_line_cmdsub2" 
time while_LINE_line_cmdsub2 >> $TIMEFILE 
echo "\nMethod 8:" 
echo "\nfunction while_LINE_line_bottom_cmdsub2\n" >> $TIMEFILE 
echo "function while_LINE_line_bottom_cmdsub2" 
time while_LINE_line_bottom_cmdsub2 >> $TIMEFILE 
echo "\nMethod 9:" 
echo "\nfunction while_read_LINE_FD\n" >> $TIMEFILE 
echo "function while_read_LINE_FD" 
time while_read_LINE_FD >> $TIMEFILE 
echo "\nMethod 10:" 
echo "\nfunction while_LINE_line_FD\n" >> $TIMEFILE 
echo "function while_LINE_line_FD" 
time while_LINE_line_FD >> $TIMEFILE 
echo "\nMethod 11:" 
echo "\nfunction while_LINE_line_cmdsub2_FD\n" >> $TIMEFILE 
echo "function while_LINE_line_cmdsub2_FD" 
time while_LINE_line_cmdsub2_FD >> $TIMEFILE 
echo "\nMethod 12:" 
echo "\nfunction while_line_LINE_FD\n" >> $TIMEFILE 
echo "function while_line_LINE_FD" 
time while_line_LINE_FD >> $TIMEFILE