Ubuntu – How to find all PDF files in directories and their subdirectories

If I understand correctly what you want to do, this is the solution:

#!/bin/sh

USAGE="Usage: $0 dir file1 file2 ... fileN\nto find all subdirectories of dir that contain all the given files.\n"

if [ "$#" == "0" ]; then
    printf "$USAGE"
    exit 1
fi

ARG=""
DIR=$1
shift

while (( "$#" )); do
  ARG="$ARG -exec test -e \"{}/$1\" \; "
  shift
done

cmd="find $DIR -type d $ARG -print"
eval $cmd

What it does is this:

The use find ... -type d to find all subdirectories (including the directory given as first parameter). The test -e command checks if a file exists. So for a given directory we have to check all the files given in the command line: test -e /path/to/directory/file1 test -e /path/to/directory/file2 test -e /path/to/directory/file3 ... The /path/to/directory is {} - a single result of find. Then the find-parameter -exec can be used to check for a single file. To check for all files several -exec test parameters are needed. So while loop build a list of there parameters, then this list is put together in a single command and evaluated.

Have fun ...

Find-based solution:

find . -maxdepth 1 -type f -printf '%f\n'

Bash-based solution:

for f in *; do [[ -d "$f" ]] || echo "$f"; done
##  or, if you want coloured output:
for f in *; do [[ -d "$f" ]] || ls -- "$f"; done

The bash-based solution will get you everything that isn't a directory; it will include things like named pipes (you probably want this). If you specifically want just files, either use the find command or one of these:

for f in *; do [[ -f "$f" ]] && echo "$f"; done
##  or, if you want coloured output:
for f in *; do [[ -f "$f" ]] && ls -- "$f"; done

If you're going to be using this regularly, you can of course put this into an alias somewhere in your ~/.bashrc:

alias lsfiles='for f in *; do [[ -f "$f" ]] && ls -- "$f"; done'

Since you noted in the comments that you're actually on OSX rather than Ubuntu, I would suggest that next time you direct questions to the Apple or more general Unix & Linux Stack Exchange sites.