quick IF question

[pickarooney]

trying to add a line in a bash script to say "if there are any files then do the following".
if I do it only for specific files it's fine - if [ -ef *.txt ]
then

but if I put in * or *.* instead of *.txt the shell interprets it as a wildcard and tries to apply it to the pwd.
Hope that makes sense.
Alternatively a multifilter like id [ -ef *.txt|*.doc|.zip ] would work, but that syntax is wrong.

[Modorf]

if [ -ef .*\..{3} ]
then


This will find all files that have == *.???
Look up regular expressions. That will explain why your have to escape code the '.'

. matches any character

n

http://tille.soti.org/training/bash/ch04.html

[bwkaz]

But test (and therefore [) don't use regular expressions...

The problem is that bash does the wildcard expansion (wildcard expansion is NOT the same as regex expansion -- regexes are more powerful in that they can match strings that wildcards can't) before the program runs. It expands *.* into all filenames containing a period anywhere in their names, and "test" errors out when there's more than one operand to -e or -f (incidentally, you can get rid of the -e test there; -f is "-e plus it's a regular file").

What you can do is:

firstfile=$(echo *.* | cut -d' ' -f 1)

if [ -f $firstfile ] ; then
# do whatever
fi This way, the argument to -f is always only one file. It will break, however, if there are any filenames with spaces in them that match your wildcard, so you'll want to be careful of that.

[pickarooney]

Tricky bugger, isn't it? :)

I used a similar clunky workaround for the time being...anyfiles=`ls|head -1`
if [ "$anyfiles" != "" ]
then
dostuff
fi

[the.spike]

Originally posted by bwkaz
"test" errors out when there's more than one operand to -e or -f

This is not strickly true.. I've just coded the following..

if [ ! -f $INPUT_FILES.Z ]
then

where INPUT_FILES="DM_ASL_G_*.DAT"

and it works a treat where there are multiple files (Had to test it as I wasn't sure that I ever had!). Could be related to the fact that I am doing a ! -f instead of a -f though...

spike...

[bwkaz]

Hmm...

[ -f one two ]

and

[ ! -f one two ]

both give:

bash: [: one: binary operator expected

while

[ -f one ]

and

[ ! -f one ]

give no output (and the return value is set appropriately).

However, it works differently when bash expands variables containing glob characters, apparently. I thought it would do glob expansion when setting the variable, but apparently it does it when evaluating the command that uses the variable. Huh.