Shell Programming and Scripting

if [ $# -eq 1 ]
  then
  cp -p $1 $1.bak
fi
/usr/bin/vi $*
if [ $# -eq 1 ]
  then
  rm $1.bak
fi

PATH=.:/usr/shells:/bin:/etc:/usr/bin:/tcb/bin:/u/wbport

if [ $# -eq 1 -a -s $1 ]

# example:
/path/to/shell.sh parameter1

shell.sh parameter1

export PATH=".:${PATH}"

which t.shl

for f
do
  [ -s "$f" ] && cp "$f" "$f.bak" && echo "created $f.bak"
done
/usr/bin/vi "$@"
for f
do
  [ -f "$f.bak" ] && rm "$f.bak" && echo "removed $f.bak"
done

vi "file name with spaces"

vi()
{
  for f in $@
  do
     [ -s "$f" ] && cp -f "$f" "$f.bak" && echo "created $f.bak"
  done

  /usr/bin/vi $@

  for f  in $@
  do
    [ -f "$f.bak" ] && rm "$f.bak" && echo "removed $f.bak"
  done
}

$ cat demo
echo '$@ - word splitting takes place'
for f in $@
do
  echo "$f"
done
echo '"$@" - quotes prevent word splitting; $@ (and [@] in arrays in later shells) split into arguments (elements) nevertheless'
for f in "$@"
do
  echo "$f"
done
$ /bin/sh demo "" 1 2 "3 4"
$@ - word splitting takes place
1
2
3
4
"$@" - quotes prevent word splitting; $@ (and [@] in arrays in later shells split into arguments (elements) nevertheless

1
2
3 4

/bin/sh demo "*"

if [ $# -eq 1 -a -s $1 ]
  then
  cp -p $1 $1.bak
echo "While using vi, $1.bak has been created."
sleep 1
fi
/usr/bin/vi $*
if [ -f $1.bak ]
  then
  rm $1.bak
fi