🚀 go-pugleaf

For the Bourne shell, try :

if [ -f file ] ; then
	mv file otherfile
fi

see test(1) for more details and other useful options.

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In article <ger.659126250@prisma> ger@prisma.cv.ruu.nl (Ger Timmens) writes:
>Can anybody tell me how I can verify whether a file exists or not ?
>I want to move files and only when they exist ! mv "file" gives an
>error message if "file" not exists 

if (-f filename) will return true if the file exists, false if not.
There are many other options for which you can also test:
-d if filename is a directory,
-z if filename is zero length,
-w if filename is writable,
etc.

RTFM!

In article <ger.659126250@prisma>, ger@prisma.cv.ruu.nl (Ger Timmens) writes:
|> Can anybody tell me how I can verify
|> whether a file exists or not ?
|> I want to move files and only when
|> they exist ! mv "file" gives an
|> error message if "file" not exists

  It depends on the shell you're using.  In csh or tcsh:

	if (-e filename) then
		... stuff if filename exists ...
	endif

In sh, with either a test built-in named "[" or a link in your filesystem
called "[" pointing to the test program:

	if [ -r filename ]; then
		... stuff if filename exists ...
	fi

Some versions of test allow "-e" to test for existence, instead of "-r" to
test for existence and readibility, but mine doesn't, so I use "-r" instead of
"-e" above.  In sh without "[":

	if test -r filename; then
		... stuff if filename exists
	fi

Ksh and bash probably do things the same way sh does, using "[".

  In the future, it would help if you would give more details, such as the
shell you're using, when you ask questions like this.
		
-- 
Jonathan Kamens			              USnail:
MIT Project Athena				11 Ashford Terrace
jik@Athena.MIT.EDU				Allston, MA  02134
Office: 617-253-8085			      Home: 617-782-0710

ger@prisma.cv.ruu.nl (Ger Timmens) writes:

>Can anybody tell me how I can verify
>whether a file exists or not ?
>I want to move files and only when
>they exist ! mv "file" gives an
>error message if "file" not exists

Try this:

if [ -f file_name ]
then
        mv file_name /new/destination/file_name
fi

The "-f" tests for the existence of the file.  There are other options:

-x  is the file executable
-r  is the file readable
-s  does the file have anything in it (greater than zero bytes)

There  are  others too.  Check your manual under "sh".  The options should  be
listed.
-- 
Bill Irwin    -       The Westrheim Group     -    Vancouver, BC, Canada
~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~
uunet!van-bc!twg!bill     (604) 431-9600 (voice) |     UNIX Systems
bill@twg.bc.ca            (604) 430-4329 (fax)   |     Integration

In article <1990Nov21.191638.19469@athena.mit.edu>, jik@athena.mit.edu (Jonathan
I. Kamens) says:
>
>In sh, with either a test built-in named "[" or a link in your filesystem
                                              ^^^^^^^^^^^^^^^^^^^^^^^^^^^
>called "[" pointing to the test program:
 ^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^^
But what will the (bourne-) shell say about...
>
>        if [ -r filename ]; then
                          ^
  ... ?

Thomas Heller

In article <1990Nov21.191638.19469@athena.mit.edu> jik@athena.mit.edu (Jonathan I. Kamens) writes:

| In sh, with either a test built-in named "[" or a link in your filesystem
| called "[" pointing to the test program:
| 
| 	if [ -r filename ]; then
| 		... stuff if filename exists ...
| 	fi
| 
| Some versions of test allow "-e" to test for existence, instead of "-r" to
| test for existence and readibility, but mine doesn't, so I use "-r" instead of
| "-e" above.  In sh without "[":
| 
| 	if test -r filename; then
| 		... stuff if filename exists
| 	fi

  Close but not correct.
	-f is there a file
	-r is it readable
	-x is it executable
-- 
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me

In article <1990Nov21.155149.3505@informix.com> dberg@informix.com (David I. Berg) writes:

| -z if filename is zero length,

  Actually -z (zero length) and -n (non-zero length) apply to any string
following the operator, although it certainly applies to filename in strings.
-- 
bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
    sysop *IX BBS and Public Access UNIX
    moderator of comp.binaries.ibm.pc and 80386 mailing list
"Stupidity, like virtue, is its own reward" -me

In article <90326.175421PPH93@DMSWWU1A.BITNET> PPH93@DMSWWU1A.BITNET (Thomas Heller) writes:

>But what will the (bourne-) shell say about...
>>
>>        if [ -r filename ]; then
>                          ^

Why should the shell do anything about it? The "]" is an argument to
"[" (which is a link to test). The shell just passes that token as an
argument when it exec's test.
    
Eduardo Krell                   AT&T Bell Laboratories, Murray Hill, NJ

UUCP: {att,decvax,ucbvax}!ulysses!ekrell  Internet: ekrell@ulysses.att.com

There's a one line solution that works with both csh & sh...
and is particularly handy in makefiles.

	[ -f foo ] && mv foo bar || echo foo does not exist

This is a handy way to deal with the yacc tokens file y.tab.h
so that you don't fire lots of extra recompilataions when everything
depends on that tokens file.

	cmp y.tab.h tokens.h && rm y.tab.h || mv y.tab.h tokens.h

Cryptic enough?
Stig

> In article <ger.659126250@prisma> ger@prisma.cv.ruu.nl (Ger Timmens) writes:
> Can anybody tell me how I can verify whether a file exists or not ?
> I want to move files and only when they exist ! mv "file" gives an
> error message if "file" not exists 

A number of poster have responded to Ger's posting by suggesting the
-f option of test (builtin or separate executable).  Most claimed this
option tests if the file exists and suggest that the manual be read.

They should read the manual which says:

	-f file   true if file exists AND is a regular file

(emphasis mine)

I.e., the -f is a filetype/existance test.  If a directory foobar
exists, test -f foobar is false; test -d foobar is true.

There are a number of filetype/existance options to test:

	-f	regular files
	-d	directory files
	-b	block special files
	-c	character special files
	-p	named pipe files (fifo's)

and on some systems:

	-????	symbolic link files

Jon

-- 
Jon LaBadie
{att, princeton, bcr, attmail!auxnj}!jonlab!jon

In <1990Nov21.155149.3505@informix.com> dberg@informix.com (David I. Berg) writes:

>if (-f filename) will return true if the file exists, false if not.

Wrong.  It will return true if the file exists AND IS A PLAIN FILE.
To test for existence only use -e.

This is one place where csh has an advantage over Bourne shell.  There is
no equivalent way with the Bourne shell "test" command to test for existence
without also testing for a specific file type or access mode.  OK, so you
can do it with

	test -f file -o -d file -o -c file -o -b file -o -p file

but I don't count that as "equivalent"!

-- 
Geoff Clare <gwc@root.co.uk>  (Dumb American mailers: ...!uunet!root.co.uk!gwc)
UniSoft Limited, Hayne Street, London EC1A 9HH, England.   Tel: +44-71-315-6600

In article <2356@sixhub.UUCP> davidsen@sixhub.UUCP (bill davidsen) writes:
>In article <1990Nov21.191638.19469@athena.mit.edu> jik@athena.mit.edu (Jonathan I. Kamens) writes:
>
>| In sh, with either a test built-in named "[" or a link in your filesystem
>| called "[" pointing to the test program:
>| 
>| 	if [ -r filename ]; then
>| 		... stuff if filename exists ...
>| 	fi
>| 
>| Some versions of test allow "-e" to test for existence, instead of "-r" to
>| test for existence and readibility, but mine doesn't, so I use "-r" instead of
>| "-e" above.  In sh without "[":
>| 
>| 	if test -r filename; then
>| 		... stuff if filename exists
>| 	fi
>
>  Close but not correct.
>	-f is there a file
>	-r is it readable
>	-x is it executable

	-s file has nonzero length

>-- 
>bill davidsen - davidsen@sixhub.uucp (uunet!crdgw1!sixhub!davidsen)
>    sysop *IX BBS and Public Access UNIX
>    moderator of comp.binaries.ibm.pc and 80386 mailing list

if [ -s $USER.IQ ]
   then 
       echo "Proceed..."
       read chore
       etc etc
   else
       echo "Stupidity, like virtue, is its own reward"
       exit 0
fi


There, now your .sig is more fitting :-)

In article <ger.659126250@prisma> ger@prisma.cv.ruu.nl (Ger Timmens) writes:
>Can anybody tell me how I can verify
>whether a file exists or not ?
>I want to move files and only when
>they exist ! mv "file" gives an
>error message if "file" not exists

Ah, the error message is the real problem here - just throw it away!
   mv old new 2>/dev/null

Note of course that you also lose "real" error messages with this
approach.  However, also keep in mind that no method of testing
before the move is atomic with the mv itself and thus will fail
with multiple concurrent processes.

Les Mikesell
  les@chinet.chi.il.us

In <14048@ulysses.att.com> ekrell@ulysses.att.com (Eduardo Krell) writes:

>Why should the shell do anything about it? The "]" is an argument to
>"[" (which is a link to test). The shell just passes that token as an
>argument when it exec's test.

Also, the test command looks at argv[0] to see if it was called "test"
or "[".  If "[" then test verifies that the closing "]" argument is there.
If the closing "]" is not there, test exits with a status of 1 (false).

Rob

>But what will the (bourne-) shell say about...
>>
>>        if [ -r filename ]; then

It'll say "OK, this 'if' is going to run the command named '[', passing
it '-r' as its first argument, 'filename' as its second argument, and
']' as its third argument."

"test"/"[" will then say "well, I was invoked as '[' rather than 'test';
that means I should check to make sure my last argument is ']', and
complain otherwise."

In article <4586@auspex.auspex.com> guy@auspex.auspex.com (Guy Harris) writes:
 >>But what will the (bourne-) shell say about...
 >>>
 >>>        If [ -r filename ]; then

 >"test"/"[" will then say "well, I was invoked as '[' rather than 'test';
 >that means I should check to make sure my last argument is ']', and
 >complain otherwise."

trying /bin/[ shows that it only checks if argv[0] == "[".

In article <2549@root44.co.uk>, gwc@root.co.uk (Geoff Clare) writes:
> 
> 	test -f file -o -d file -o -c file -o -b file -o -p file
> 
> but I don't count that as "equivalent"!
> 

OK, granted, but how about the nearly equivalent

	test ! -f file

It will be true when you want a regular file of the indicated name
and false if said file does not exist or is a type other than regular.

Another possibility not mentioned in this thread (and with its own
limitations) is test -s file.  For this to be true, the file must
exist and have some content (i.e. not an empty file).

Jon

-- 
Jon LaBadie
{att, princeton, bcr, attmail!auxnj}!jonlab!jon

In article <1779@seti.inria.fr>
deschamp@minos.inria.fr (Philippe Deschamp) writes:
>In article <QPLIU.90Nov29205347@phoenix.princeton.edu>,
>qpliu@phoenix.princeton.edu (q.p.liu) writes:
>|> trying /bin/[ shows that it only checks if argv[0] == "[".
>   *Never* generalize :-). On my workstation (Sun 3/60 under SunOS 4.0.3):

(Ok, was on sunos 4.1, 4.0.3 (sun4) and ctss (cray xmp, cray 2) running sh)

(btw, the string comparision is as in awk, not as in C)

>What I do not understand is this:
>	$ /bin/[
>	$
>
>Why no complaint in the last case ?

In this case, argv[0] != "[", hence no check for ].

In article <QPLIU.90Nov29205347@phoenix.princeton.edu>, qpliu@phoenix.princeton.edu (q.p.liu) writes:
|> In article <4586@auspex.auspex.com> guy@auspex.auspex.com (Guy Harris) writes:
|>  >"test"/"[" will then say "well, I was invoked as '[' rather than 'test';
|>  >that means I should check to make sure my last argument is ']', and
|>  >complain otherwise."
|> trying /bin/[ shows that it only checks if argv[0] == "[".

  Then either you did something wrong, or you're using a buggy version of
"test."

	$ [ frep
	test: ] missing
	$ echo $?
	255
	$ [ frep ]
	$ echo $?
	0

-- 
Jonathan Kamens			              USnail:
MIT Project Athena				11 Ashford Terrace
jik@Athena.MIT.EDU				Allston, MA  02134
Office: 617-253-8085			      Home: 617-782-0710

In article <1990Dec2.210141.13170@athena.mit.edu>, I write:
|> In article <QPLIU.90Nov29205347@phoenix.princeton.edu>, qpliu@phoenix.princeton.edu (q.p.liu) writes:
|> |> trying /bin/[ shows that it only checks if argv[0] == "[".
|> 
|>   Then either you did something wrong, or you're using a buggy version of
|> "test."

  I corrected q.p.liu because I misunderstood what he was saying, and just
realized this, so I'd like to apologize.  He was saying, "`Test' only checks
if the final `]' is present if it is invoked with argv[0] exactly equal to
`['."  I thought he was saying, "`Test' only checks if its argv[0] is exactly
equal to `['; it does not also check if the final ']' is present."

  Liu is right, of course.  Whether or not this behavior of "test" (i.e. the
distinguishing between "[" and "/bin/[") is correct is debatable, but I
believe that it is.

-- 
Jonathan Kamens			              USnail:
MIT Project Athena				11 Ashford Terrace
jik@Athena.MIT.EDU				Allston, MA  02134
Office: 617-253-8085			      Home: 617-782-0710

In article <1779@seti.inria.fr> deschamp@seti.inria.fr writes:
:
:In article <QPLIU.90Nov29205347@phoenix.princeton.edu>,
:qpliu@phoenix.princeton.edu (q.p.liu) writes:
:
:|> trying /bin/[ shows that it only checks if argv[0] == "[".
:
:   *Never* generalize :-). On my workstation (Sun 3/60 under SunOS 4.0.3):
:	$ test
:	$ [
:	test: ] missing
:
:What I do not understand is this:
:	$ '['
:	test: ] missing
:	$ PATH=/bin '['
:	test: ] missing
:	$ /bin/[
:	$
:
:Why no complaint in the last case ?

This shows exactly what original poster tried to say (as I understood).
To make it a bit clearer, the source-code of "test" must look like

	if (!strcmp(argv[0], "[")) {
		if (strcmp(argv[--argc], "]") {
			/* complain about missing "]" and exit */
			.....
		}
	}
	/* parse arguments; run tests as required */
	.....

In your last experiment argv[0] is "/bin/[" and not simply "[", hence no
comlaint.
-- 
Martin Weitzel, email: martin@mwtech.UUCP, voice: 49-(0)6151-6 56 83