Answer:
#!/bin/bash
# Simple line count example, using bash
# Usage: ./line_count.sh file
# -----------------------------------------------------------------------------
# Link filedescriptor 10 with stdin
exec 10<&0
# stdin replaced with a file supplied as a first argument
exec < $1
# remember the name of the input file
in=$1
# init
file="current_line.txt"
let count=0
# this while loop iterates over all lines of the file
while read LINE
do
# increase line counter
((count++))
# write current line to a tmp file with name $file (not needed for counting)
echo $LINE > $file
# this checks the return code of echo (not needed for writing; just for demo)
if [ $? -ne 0 ]
then echo "Error in writing to file ${file}; check its permissions!"
fi
done
echo "Number of lines: $count"
echo "The last line of the file is: `cat ${file}`"
# Note: You can achieve the same by just using the tool wc like this
echo "Expected number of lines: `wc -l $in`"
# restore stdin from filedescriptor 10
# and close filedescriptor 10
exec 0<&10 10<&-
Explanation:
