|
Size: 2217
Comment: put bash solutions at top, removed bash-specific non-array solution (what's wrong with arrays?), removed ls -A solutions (if you want to not use a specific shell you may as well TRY to be portable)
|
Size: 2262
Comment:
|
| Deletions are marked like this. | Additions are marked like this. |
| Line 1: | Line 1: |
| [[Anchor(faq4)]] | <<Anchor(faq4)>> |
| Line 3: | Line 3: |
| ''I just deleted three completely '''wrong''' answers from this question. Please, people, make sure that when you add to the FAQ, your answers'' * answer the question that was asked, and * actually '''work''' ''Thanks. -- GreyCat'' In BASH, you can do this safely and easily with the nullglob option (which changes the behaviour of [:glob:globbing]), and arrays: |
In Bash, you can do this safely and easily with the `nullglob` and `dotglob` options (which change the behaviour of [[glob|globbing]]), and [[BashFAQ/005|arrays]]: |
| Line 11: | Line 6: |
| shopt -s nullglob | # Bash shopt -s nullglob dotglob |
| Line 14: | Line 10: |
| shopt -u nullglob | shopt -u nullglob dotglob |
| Line 20: | Line 16: |
| # Bash | |
| Line 30: | Line 27: |
| # Bash | |
| Line 38: | Line 36: |
| In fact, you may wish to avoid the ''direct'' question altogether. Usually people want to know whether a directory is empty... ''because'' they want to do something involving the files therein, etc. Look to the larger question. For example, one of these [:UsingFind:find-based examples] may be an appropriate solution: | In fact, you may wish to avoid the ''direct'' question altogether. Usually people want to know whether a directory is empty... ''because'' they want to do something involving the files therein, etc. Look to the larger question. For example, one of these [[UsingFind|find-based examples]] may be an appropriate solution: |
| Line 41: | Line 39: |
| # Bourne | |
| Line 49: | Line 48: |
| if [ "`printf %s foo/*`" = 'foo/*' ] && [ ! -e 'foo/*' ] | # Bourne # (Of course, the system must have printf(1).) cd foo || exit 1 if test "`printf '%s %s %s' .* *`" = '. .. *' && test ! -f '*' |
| Line 51: | Line 53: |
| echo "foo is empty" | echo "directory is empty" |
| Line 55: | Line 57: |
| Yes, it's ugly, but it should be more portable than anything depending on ls output. | Yes, it's extremely ugly, but it should be more portable than anything depending on [[ParsingLs|ls output]]. Even `ls -A` solutions can break (HPUX for one, if you are root). |
How can I check whether a directory is empty or not? How do I check for any *.mpg files?
In Bash, you can do this safely and easily with the nullglob and dotglob options (which change the behaviour of globbing), and arrays:
# Bash
shopt -s nullglob dotglob
files=(*)
(( ${#files[*]} )) || echo directory is empty
shopt -u nullglob dotglobAs you can see we unset the nullglob after using it, to prevent it affecting other globs in the script in unexpected ways. nullglob also simplifies various other operations:
# Bash
shopt -s nullglob
for i in *.zip; do
blah blah "$i" # No need to check $i is a file.
done
shopt -u nullglobWithout the nullglob, that would have to be:
# Bash
for i in *.zip; do
[[ -f $i ]] || continue # If no .zip files, i becomes *.zip
blah blah "$i"
done(You may want to use the latter anyway, if there's a possibility that the glob may match directories in addition to files.)
In fact, you may wish to avoid the direct question altogether. Usually people want to know whether a directory is empty... because they want to do something involving the files therein, etc. Look to the larger question. For example, one of these find-based examples may be an appropriate solution:
# Bourne
find "$somedir" -type f -exec echo Found unexpected file {} \;
find "$somedir" -maxdepth 0 -empty -exec echo {} is empty. \; # GNU/BSD
find "$somedir" -type d -empty -exec cp /my/configfile {} \; # GNU/BSDIf your script needs to run with various shell implementations, you can try using an external program like python, perl, or find as indicated above, or you can try something like:
# Bourne
# (Of course, the system must have printf(1).)
cd foo || exit 1
if test "`printf '%s %s %s' .* *`" = '. .. *' && test ! -f '*'
then
echo "directory is empty"
fiYes, it's extremely ugly, but it should be more portable than anything depending on ls output. Even ls -A solutions can break (HPUX for one, if you are root).