Test multiple file conditions in one swoop (BASH)? - bash

Question

Often when writing for the bash shell, one needs to test if a file (or Directory) exists (or doesn't exist) and take appropriate action. Most common amongst these test are...
-e - file exists, -f - file is a regular file (not a directory or device file), -s - file is not zero size, -d - file is a directory, -r - file has read permission, -w - file has write, or -x execute permission (for the user running the test)
This is easily confirmed as demonstrated on this user-writable directory....
#/bin/bash
if [ -f "/Library/Application Support" ]; then
echo 'YES SIR -f is fine'
else echo 'no -f for you'
fi
if [ -w "/Library/Application Support" ]; then
echo 'YES SIR -w is fine'
else echo 'no -w for you'
fi
if [ -d "/Library/Application Support" ]; then
echo 'YES SIR -d is fine'
else echo 'no -d for you'
fi
➝ no -f for you ✓
➝ YES SIR -w is fine ✓
➝ YES SIR -d is fine ✓
My question, although seemingly obvious, and unlikely to be impossible - is how to simply combine these tests, without having to perform them separately for each condition... Unfortunately...
if [ -wd "/Library/Application Support" ]
▶ -wd: unary operator expected
if [ -w | -d "/Library/Application Support" ]
▶ [: missing `]'
▶ -d: command not found
if [ -w [ -d "/Library.... ]] & if [ -w && -d "/Library.... ]
▶ [: missing `]'
➝ no -wd for you ✖
➝ no -w | -d for you ✖
➝ no [ -w [ -d .. ]] for you ✖
➝ no -w && -d for you ✖
What am I missing here?

Answer 1

You can use logical operators to multiple conditions, e.g. -a for AND:
MYFILE=/tmp/data.bin
if [ -f "$MYFILE" -a -r "$MYFILE" -a -w "$MYFILE" ]; then
#do stuff
fi
unset MYFILE

Answer 2

Of course, you need to use AND somehow as Kerrek(+1) and Ben(+1) pointed it out. You can do in in few different ways. Here is an ala-microbenchmark results for few methods:
Most portable and readable way:
$ time for i in $(seq 100000); do [ 1 = 1 ] && [ 2 = 2 ] && [ 3 = 3 ]; done
real 0m2.583s
still portable, less readable, faster:
$ time for i in $(seq 100000); do [ 1 = 1 -a 2 = 2 -a 3 = 3 ]; done
real 0m1.681s
bashism, but readable and faster
$ time for i in $(seq 100000); do [[ 1 = 1 ]] && [[ 2 = 2 ]] && [[ 3 = 3 ]]; done
real 0m1.285s
bashism, but quite readable, and fastest.
$ time for i in $(seq 100000); do [[ 1 = 1 && 2 = 2 && 3 = 3 ]]; done
real 0m0.934s
Note, that in bash, "[" is a builtin, so bash is using internal command not a symlink to /usr/bin/test exacutable. The "[[" is a bash keyword. So the slowest possible way will be:
time for i in $(seq 100000); do /usr/bin/\[ 1 = 1 ] && /usr/bin/\[ 2 = 2 ] && /usr/bin/\[ 3 = 3 ]; done
real 14m8.678s

Answer 3

You want -a as in -f foo -a -d foo (actually that test would be false, but you get the idea).
You were close with & you just needed && as in [ -f foo ] && [ -d foo ] although that runs multiple commands rather than one.
Here is a manual page for test which is the command that [ is a link to. Modern implementations of test have a lot more features (along with the shell-builtin version [[ which is documented in your shell's manpage).

Answer 4

check-file(){
while [[ ${#} -gt 0 ]]; do
case $1 in
fxrsw) [[ -f "$2" && -x "$2" && -r "$2" && -s "$2" && -w "$2" ]] || return 1 ;;
fxrs) [[ -f "$2" && -x "$2" && -r "$2" && -s "$2" ]] || return 1 ;;
fxr) [[ -f "$2" && -x "$2" && -r "$2" ]] || return 1 ;;
fr) [[ -f "$2" && -r "$2" ]] || return 1 ;;
fx) [[ -f "$2" && -x "$2" ]] || return 1 ;;
fe) [[ -f "$2" && -e "$2" ]] || return 1 ;;
hf) [[ -h "$2" && -f "$2" ]] || return 1 ;;
*) [[ -e "$1" ]] || return 1 ;;
esac
shift
done
}
check-file fxr "/path/file" && echo "is valid"
check-file hf "/path/folder/symlink" || { echo "Fatal error cant validate symlink"; exit 1; }
check-file fe "file.txt" || touch "file.txt" && ln -s "${HOME}/file.txt" "/docs/file.txt" && check-file hf "/docs/file.txt" || exit 1
if check-file fxrsw "${HOME}"; then
echo "Your home is your home from the looks of it."
else
echo "You infected your own home."
fi

Answer 5

Why not write a function to do it?
check_file () {
local FLAGS=$1
local PATH=$2
if [ -z "$PATH" ] ; then
if [ -z "$FLAGS" ] ; then
echo "check_file: must specify at least a path" >&2
exit 1
fi
PATH=$FLAGS
FLAGS=-e
fi
FLAGS=${FLAGS#-}
while [ -n "$FLAGS" ] ; do
local FLAG=`printf "%c" "$FLAGS"`
if [ ! -$FLAG $PATH ] ; then false; return; fi
FLAGS=${FLAGS#?}
done
true
}
Then just use it like:
for path in / /etc /etc/passwd /bin/bash
{
if check_file -dx $path ; then
echo "$path is a directory and executable"
else
echo "$path is not a directory or not executable"
fi
}
And you should get:
/ is a directory and executable
/etc is a directory and executable
/etc/passwd is not a directory or not executable
/bin/bash is not a directory or not executable

Answer 6

This seems to work (notice the double brackets):
#!/bin/bash
if [[ -fwd "/Library/Application Support" ]]
then
echo 'YES SIR -f -w -d are fine'
else
echo 'no -f or -w or -d for you'
fi