检查目录中是否存在特定的文件类型/扩展名

You need to be carful which flag you throw into your if statement, and how it relates to the outcome you want.

If you want to check for only regular files and not other types of file system entries then you'll want to change your code skeleton to:

if [ -f file ]; then
echo true;
fi

The use of the -f restricts the if to regular files, whereas -e is more expansive and will match all types of filesystem entries. There are of course other options like -d for directories, etc. See http://tldp.org/LDP/abs/html/fto.html for a good listing.

As pointed out by @msw, test (i.e. [) will choke if you try and feed it more than one argument. This might happen in your case if the glob for *.flac returned more than one file. In that case try wrapping your if test in a loop like:

for file in ./*.pdf
do
if [ -f "${file}" ]; then
echo 'true';
break
fi
done

This way you break on the first instance of the file extension you want and can keep on going with the rest of the script.

#!/bin/bash
files=$(ls /home/somedir/*.flac 2> /dev/null | wc -l)
if [ "$files" != "0" ]
then
echo "Some files exists."
else
echo "No files with that extension."
fi

#!/bin/bash


count=`ls -1 *.flac 2>/dev/null | wc -l`
if [ $count != 0 ]
then
echo true
fi

#/bin/bash


myarray=(`find ./ -maxdepth 1 -name "*.py"`)
if [ ${#myarray[@]} -gt 0 ]; then
echo true
else
echo false
fi

   shopt -s nullglob
set -- $(echo *.ext)
if [ "${#}" -gt 0 ];then
echo "got file"
fi

bash only:

any_with_ext () (
ext="$1"
any=false
shopt -s nullglob
for f in *."$ext"; do
any=true
break
done
echo $any
)


if $( any_with_ext flac ); then
echo "have some flac"
else
echo "dir is flac-free"
fi

I use parentheses instead of braces to ensure a subshell is used (don't want to clobber your current nullglob setting).

shopt -s nullglob
if [[ -n $(echo *.flac) ]]    # or [ -n "$(echo *.flac)" ]
then
echo true
fi

This uses ls(1), if no flac files exist, ls reports error and the script exits; othewise the script continues and the files may be be processed

#! /bin/sh
ls *.flac  >/dev/null || exit
## Do something with flac files here

The top solution (if [ -e *.flac ];) did not work for me, giving: [: too many arguments

if ls *.flac >/dev/null 2>&1; then it will work.

Here is a solution using no external commands (i.e. no ls), but a shell function instead. Tested in bash:

shopt -s nullglob
function have_any() {
[ $# -gt 0 ]
}


if have_any ./*.flac; then
echo true
fi

The function have_any uses $# to count its arguments, and [ $# -gt 0 ] then tests whether there is at least one argument. The use of ./*.flac instead of just *.flac in the call to have_any is to avoid problems caused by files with names like --help.

You can use -f to check whether files of a specific type exist:

#!/bin/bash


if [ -f *.flac ] ; then
echo true
fi

For completion, with zsh:

if [[ -n *.flac(#qN) ]]; then
echo true
fi

This is listed at the end of the Conditional Expressions section in the zsh manual. Since [[ disables filename globbing, we need to force filename generation using (#q) at the end of the globbing string, then the N flag (NULL_GLOB option) to force the generated string to be empty in case there’s no match.

Here's a fairly simple solution:

if [ "$(ls -A | grep -i \\.flac\$)" ]; then echo true; fi

As you can see, this is only one line of code, but it works well enough. It should work with both bash, and a posix-compliant shell like dash. It's also case-insensitive, and doesn't care what type of files (regular, symlink, directory, etc.) are present, which could be useful if you have some symlinks, or something.

I tried this:

if [ -f *.html ]; then
echo "html files exist"
else
echo "html files dont exist"
fi

I used this piece of code without any problem for other files, but for html files I received an error:

[: too many arguments

I then tried @JeremyWeir's count solution, which worked for me:

count=`ls -1 *.flac 2>/dev/null | wc -l`
if [ $count != 0 ]
then
echo true
fi

Keep in mind you'll have to reset the count if you're doing this in a loop:

count=$((0))

This should work in any borne-like shell out there:

if [ "$(find . -maxdepth 1 -type f | grep -i '.*\.flac$')" ]; then
echo true
fi

This also works with the GNU find, but IDK if this is compatible with other implementations of find:

if [ "$(find . -maxdepth 1 -type f -iname \*.flac)" ]; then
echo true
fi