[Solved] Shell: Is there a difference between / and // in directories?

Question

Hello:
I'm making this tiny program in Shell:
# Function.
# NAME: chk_df
# Synopsis:
# Check if a local directory (dirName) exist and has a file (fileName).
# The return codes are the following:
# 99 : dirName does not exists
# 0 : dirName exists and has fileName
# 1 : dirName exists and has not fileName
# Parameters:
# In values: dirName <string> fileName <string>
# Out values: returnCode <int>
# How to use:
# chk_df dirName fileName
chk_df(){
# Check the number of arguments that could be passed.
# In this case, two, dirName, fileNAme.
if [[ ${#@} != 2 ]]; then
echo "Error ...Use [Funtion]: chk_df <dirName> <fileName>"
echo "Ex: chk_df /foo lola.txt"
exit
fi
DIR=$1
FILE=$2
[[ ! -d $DIR ]] && return 99
[[ -d $DIR && ! -e $DIR/$FILE ]] && return 1
[[ -d $DIR && -e $DIR/$FILE ]] && return 0
Because I need to check if a file is in a directory, I did this (horrible?) patch $DIR/$FILE , but things like this could happen:
I) If we do: chk_df /foo lola.txt
We get: /foo/lola.txt
II) If we do: chk_df /foo/ lola.txt
We get: /foo//lola.txt [Notice the //]
In both cases the code seems to work. Why?
Could I leave it like that or it will bring problems? Is there a difference? UNIX assume it to the right way?
EXTRA QUESTION: why I can not do the returns with negative numbers? This is:   return -1
Thank you.
Last edited by gromlok (2011-11-07 15:48:44)

Answer 1

If this script is bash only, you could use bash parameter expansion to get rid of any number of //:
$ DIR="/long//numerous//doubleslashed/path/to/"
$ FILE="file"
$ MYPATH="$DIR/$FILE"
$ cd $MYPATH
bash: cd: /long//numerous//doubleslashed/path/to//file: No such file or directory
$ cd ${MYPATH//\/\//\/}
bash: cd: /long/numerous/doubleslashed/path/to/file: No such file or directory
See http://mywiki.wooledge.org/BashGuide/Pa … _Expansion if you want a better explanation.
Edit: changed variable name from PATH to MYPATH.  Boy was I surprised by bash: pacman: command not found
Last edited by alphaniner (2011-11-07 17:26:02)