open and read text file
in [Perl]
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From: cerr on 12 Mar 2010 16:40 Hi There, I'm just trying to open a text file and print line by line. My Code: my $HANDLE = $filename; open(HANDLE) or die("Could not open GPS source file."); foreach $line (<HANDLE>) { print $line; print $client $line; sleep(1); } close(HANDLE); My Problem: The script keeps dying on open(). :( The pernmissions of the file are set to -rw-r--r-- So what is the problem here? Not getting it... Thanks, Ron
From: John Bokma on 12 Mar 2010 17:15 cerr <ron.eggler(a)gmail.com> writes: > Hi There, > > I'm just trying to open a text file and print line by line. > My Code: > my $HANDLE = $filename; > open(HANDLE) or die("Could not open GPS source file."); open my $fh, '<', $filename or die "Can't open '$filename' for reading: $!"; ^^^^ ^^^^^^^^^ ^^^^^^^ ^^ Make sure to always add all four items marked with ^ > foreach $line (<HANDLE>) { > print $line; > print $client $line; while ( my $line = <$fh> ) { print $line; print $client $line; > > sleep(1); why? > } > close(HANDLE); I also check close, i.e. close $fh or die "Can't close '$filename' after reading: $!"; ^^^^^ ^^^^^^^^^ ^^^^^^^ ^^ Notice again those four items. -- John Bokma j3b Hacking & Hiking in Mexico - http://johnbokma.com/ http://castleamber.com/ - Perl & Python Development
From: Martijn Lievaart on 12 Mar 2010 17:23 On Fri, 12 Mar 2010 13:40:47 -0800, cerr wrote: > Hi There, > > I'm just trying to open a text file and print line by line. My Code: > my $HANDLE = $filename; > open(HANDLE) or die("Could not open GPS source file."); my $handle; open($handle, "<", $filename) or die("Could not open GPS source file: $!"); > > foreach $line (<HANDLE>) { for my $line (<$handle) { > print $line; > print $client $line; > > sleep(1); Why the sleep????? HTH, M4
From: cerr on 12 Mar 2010 17:29 On Mar 12, 2:23 pm, Martijn Lievaart <m...(a)rtij.nl.invlalid> wrote: > On Fri, 12 Mar 2010 13:40:47 -0800, cerr wrote: > > Hi There, > > > I'm just trying to open a text file and print line by line. My Code: > > my $HANDLE = $filename; > > open(HANDLE) or die("Could not open GPS source file."); > > my $handle; > open($handle, "<", $filename) or die("Could not open GPS source file: > $!"); > > > foreach $line (<HANDLE>) { > > for my $line (<$handle) { > > > print $line; > > print $client $line; > > > sleep(1); > > Why the sleep????? Because i wannt print one line per second only ;) Thanks Martjin and John, I got it going now!!! -- cerr
From: Jens Thoms Toerring on 12 Mar 2010 17:45
cerr <ron.eggler(a)gmail.com> wrote: > I'm just trying to open a text file and print line by line. > My Code: > my $HANDLE = $filename; > open(HANDLE) or die("Could not open GPS source file."); > foreach $line (<HANDLE>) { > print $line; > print $client $line; > > sleep(1); > } > close(HANDLE); > My Problem: > The script keeps dying on open(). :( > The pernmissions of the file are set to -rw-r--r-- > So what is the problem here? Not getting it... Because your use of open() is completely broken. No kind of open() function I have ever seen (as far as I remember) works like that. All take a file name and return a handle that in subsequent calls of functions to read from or write to the file etc. is used. A handle is something very different from the file's name (with the UNIX open() function it's an integer, with C's fopen() function it's a pointer to some structure) - and in Perl it's something you don't need to worry about;-) And open() functions typically also take at least one more argument that tells for what purpose the file is to be opened for (i.e. for reading, writing or both - that makes a lot of a difference when you have e.g. permission to read from but not to write to the file) etc. And sometimes even additional flags can or have to be given. If you want a file opened for reading do open my $handle, '<', $filename or die "Can't open file\n"; while ( my $line = <$handle> ) { ... } close $handle; The first argument to open() is the variable that, after a successful call of open(), contains the handle for the file. The second, '<', tells that you want it to be opened for reading (use '>' for writing, but there are a number of further possibilities, see 'perldoc -f open' for all the gory details). And the third is the file name (or, with other second arguments, it could be a program that then gets run and from which you want to read its output or to which you want to send data). BTW, if I remember correctly, the difference between for my $line ( <> ) { ... } and while ( my $line = <> ) { ... } is that with 'for' the '<>' is used in list context, so the whole file has to be read in immediately and thus stored in memory as a whole. This normally doesn't make much sense. With 'while' it gets read in line by line instead, so only a single line has to be kept in memory. Regards, Jens -- \ Jens Thoms Toerring ___ jt(a)toerring.de \__________________________ http://toerring.de |