In any other shell this will produce an error if there is more than one file present. If this works in a Korn shell it is probably because it is secretly using a shell builtin.
Quote:
It works in Posix shells but gives a syntax error in normal ksh88.
ksh: test: argument expected
What shell are you using (pdksh?) on what platform? If not pdksh, what does man test say?
My example was from ksh88 on HP-UX. Neither "man ksh" nor "man test" mention "test -e". Though I don't expect to find "test -e" in "ksh", many recent posts show that there are some variants out there.
The "test" command is both a "ksh" builtin and an external command.
Interesting, since this means that the implementation of ksh88 on HP-UX is not fully posix compliant.
They must be using a very early implementation where -a was used instead of -e, which was later deprecated.
Interestingly man sh-posix does mention -e . So one would have to use /bin/sh to get that functionality (or use /usr/dt/bin/dtksh of course)
Code:
test [expr]
*
Evaluate conditional expression expr. See test(1) for usage and description. The arithmetic comparison operators are not restricted to integers.
They allow any arithmetic expression. The following additional primitive expressions are allowed:
-L file
True if file is a symbolic link.
-e file
True if file exists.
file1 -nt file2
True if file1 is newer than file2.
file1 -ot file2
True if file1 is older than file2.
file1 -ef file2
True if file1 has the same device and i-node number as file2.
Last edited by Scrutinizer; 10-14-2010 at 09:57 AM..
Scrutinizer is quite correct. The filename expansion is taking place first and creating a long [ -e ] statement.
On my tests, a "test -f" is only actually testing the first name in the expanded list! If we seed the test with discrete filenames we get some unusual behavior:
Code:
touch testfile1
echo "List of files"
ls testfil*
echo ""
#
echo "Testing testfile2 then testfile1"
if [ -f testfile2 testfile1 ]
then
echo "ok"
else
echo "not ok"
fi
echo ""
echo "Testing testfile1 then testfile2"
if [ -f testfile1 testfile2 ]
then
echo "ok"
else
echo "not ok"
fi
List of files
testfile1
Testing testfile2 then testfile1
not ok
Testing testfile1 then testfile2
ok
Therefore those methods which either count the number of files or process each file in a loop are preferable. If nothing else because some implementations of "ksh" don't seem to cope with the expanded list.
Footnote: ksh88 is definitely not Posix compliant. Many standards have come and gone (including past failed Posix standards) since ksh88 was released. I find ksh88 to be pretty standard across multiple platforms of multiple vintages and continue to wait for a viable replacement cross-platform standard.
An early proposal used the KornShell -a primary (with the same meaning), but this was changed to -e because there were concerns about the high probability of humans confusing the -a primary with the -a binary operator.
Additional information on the differences: sh-posix(1)
posix shell was largely derived from ksh88, so while ksh88 is not fully compliant, but I think there are not many differences and ksh88 is largely a superset, but obviously not completely and less than I thought.
Quote:
Originally Posted by methyl
Footnote: ksh88 is definitely not Posix compliant. Many standards have come and gone (including past failed Posix standards) since ksh88 was released. I find ksh88 to be pretty standard across multiple platforms of multiple vintages and continue to wait for a viable replacement cross-platform standard.
So I found out . This is even wrong in O'Reilly's learning the Korn Shell
About the cross-platformness: If you are willing to give up goodies like arrays, then you could use posix standard and use the posix implementations on the various platforms (/bin/sh on hpux, /usr/xpg4/bin/sh on Solaris).. At least then your scripts will work on modern implementations too). You could also standardize on ksh93 (which is available as /bin/ksh93 or /usr/dt/bin/dtksh), which is also fully POSIX compliant (and is free downloadable software anyway nowadays).
S.
---------- Post updated at 16:23 ---------- Previous update was at 15:54 ----------
So in the case of a POSIX-compliant shell you can use:
Code:
exists()
{
[ -e "$1" ]
}
in case of original version of ksh88:
Code:
exists()
{
[ -a "$1" ]
}
If you want to only test for a regular file (and not a directory for example) you could do something like this:
Code:
file_exists(){
until [ -f "$1" ] ; do
[ $# -le 1 ] && return 1
shift
done
}
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1 V N(,)'1 0.2904
2 V N(,)'2 0.3180
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<<
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temp/new/b.c
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10-14-2010
. This is even wrong in O'Reilly's learning the Korn Shell