Safe File Handling

[CloneArmyCommander]

Problem

I just accidently clobbered a file I worked hours to code (luckily I have two backups, one on my computer and another on a web server, and a hard copy).

Question

When creating a file through perl, is there a way to check if a file by that name already exists, and complain if it does exist.

I have an idea, but I am looking for a quick solution. I think I could pack some code in that opens the current directory, and tests the given name against all of the files in the directory.

Is there a quicker fix than me having to kluge that in.

2005-11-06 Retitled by planetscape, as per Monastery guidelines
Original title: 'Safe File Hadling'

[tinita]

see perldoc -f -X, especially -f/-e/-d

update: perldoc perlfunc is a good start to search for a builtin function in perl.

[CloneArmyCommander]

Thanks :D!

[gloryhack]

See perldoc perlopentut, where in addition to many useful nuggets, you'll find this one:

sysopen(FH, $path, O_WRONLY | O_EXCL | O_CREAT);

[CloneArmyCommander]

Thank you :D!

[EvanCarroll]

You might also want to check out the -i flag on perl. While I know you said 'creating a file through perl' it would seem that -i might be worth knowing.


-i[extension]   edit <> files in place (makes backup if extension supp
+lied)

[vek]

The -e filetest will give you what you need.

my $filename = 'somefilename';

if (-e $filename) {
   print "File $filename already exists.\n";
} else {
   # create the file here...
}

[Anonymous Monk]

once you are set to the right path there are a variety of file tests available, one of which is -e to test if it exists. Usage could look like: die "Don't overwrite a file that already exists\n" if -e $filename; Being new to this myself I had to open up the llama book for reference (its chapter 11, page 155 of the 4th edition) or hidden in chapter 3 of the cammel.