Bash Script: unary operator expected error? - bash

Question

#!/usr/bin/env bash
FILETYPES=( "*.html" "*.css" "*.js" "*.xml" "*.json" )
DIRECTORIES=`pwd`
MIN_SIZE=1024
for currentdir in $DIRECTORIES
do
for i in "${FILETYPES[#]}"
do
find $currentdir -iname "$i" -exec bash -c 'PLAINFILE={};GZIPPEDFILE={}.gz; \
if [ -e $GZIPPEDFILE ]; \
then if [ `stat --printf=%Y $PLAINFILE` -gt `stat --printf=%Y $GZIPPEDFILE` ]; \
then gzip -k -4 -f -c $PLAINFILE > $GZIPPEDFILE; \
fi; \
elif [ `stat --printf=%s $PLAINFILE` -gt $MIN_SIZE ]; \
then gzip -k -4 -c $PLAINFILE > $GZIPPEDFILE; \
fi' \;
done
done
This script compresses all web static files using gzip. When I try to run it, I get this error bash: line 5: [: 93107: unary operator expected. What is going wrong in this script?

Answer 1

You need to export the MIN_SIZE variable. The bash you are having find spawn doesn't have a value for it so the script runs (as I just mentioned in my comment on #ooga's answer) [ $result_from_stat -gt ] which is an error and (when the result is 93107) gets you [ 93107 -gt ] which (if you run that in your shell) gets you output of:
$ [ 93107 -gt ]
-bash: [: 93107: unary operator expected

Answer 2

This could be simpler:
#!/usr/bin/env bash
FILETYPES=(html css js xml json)
DIRECTORIES=("$PWD")
MIN_SIZE=1024
IFS='|' eval 'FILTER="^.*[.](${FILETYPES[*]})\$"'
for DIR in "${DIRECTORIES[#]}"; do
while IFS= read -ru 4 FILE; do
GZ_FILE=$FILE.gz
if [[ -e $GZ_FILE ]]; then
[[ $GZ_FILE -ot "$FILE" ]] && gzip -k -4 -c "$FILE" > "$GZ_FILE"
elif [[ $(exec stat -c '%s' "$FILE") -ge MIN_SIZE ]]; then
gzip -k -4 -c "$FILE" > "$GZ_FILE"
fi
done 4< <(exec find "$DIR" -mindepth 1 -type f -regextype egrep -iregex "$FILTER")
done
There's no need to use pwd. You can just have $PWD. And probably what you needed was an array variable as well.
Instead of calling bash multiple times as an argument to find with static string commands, just read input from a pipe or better yet from a named pipe through process substitution.
Instead of comparing stats, you can just use -ot or -nt.
You don't need -f if you're writing the output through redirection (>) as that form of redirection overwrites the target by default.
You can just call find against multiple files once by making a pattern as it's more efficient. You can check how I made the filter and used -iregex. Probably doing \( -iname one_ext_pat -or -iname another_ext_pat \) can also be applicable but it's more difficult.
exec is optional to prevent unnecessary use of another process.
Always prefer [[ ]] over [ ].
4< opens input with file descriptor 4 and -u 4 makes read read from that file descriptor, not stdin (0).
What you probably need is -ge MIN_SIZE (greater than or equal) not -gt.
Come to think of it, readarray is a cleaner option if your bash is version 4.0 or newer:
for DIR in "${DIRECTORIES[#]}"; do
readarray -t FILES < <(exec find "$DIR" -mindepth 1 -type f -regextype egrep -iregex "$FILTER")
for FILE in "${FILES[#]}"; do
...
done
done