#!/bin/bash
# upperconv.sh
# Converts a specified input file to uppercase.
E_FILE_ACCESS=70
E_WRONG_ARGS=71
if [ ! -r "$1" ] # Is specified input file readable?
then
echo "Can't read from input file!"
echo "Usage: $0 input-file output-file"
exit $E_FILE_ACCESS
fi # Will exit with same error
#+ even if input file ($1) not specified.
if [ -z "$2" ]
then
echo "Need to specify output file."
echo "Usage: $0 input-file output-file"
exit $E_WRONG_ARGS
fi
exec 4<&0
exec < $1 # Will read from input file.
exec 7>&1
exec > $2 # Will write to output file.
# Assumes output file writable (add check?).
# -----------------------------------------------
cat - | tr a-z A-Z # Uppercase conversion.
# ^^^^^ # Reads from stdin.
# ^^^^^^^^^^ # Writes to stdout.
# However, both stdin and stdout were redirected.
# -----------------------------------------------
exec 1>&7 7>&- # Restore stout.
exec 0<&4 4<&- # Restore stdin.
# After restoration, the following line prints to stdout as expected.
echo "File \"$1\" written to \"$2\" as uppercase conversion."
exit 0
