Weird Character in File Makes Perl Think it's EOF


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Weird Character in File Makes Perl Think it's EOF

by davemabe (Monk)

on Oct 15, 2008 at 21:01 UTC ( [id://717343]=perlquestion: print w/replies, xml )

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davemabe has asked for the wisdom of the Perl Monks concerning the following question:

I've got some files that I'm trying to parse and there's a \032 character (ASCII 26 (EOF)) in there that is making Perl think that it's the end of the file. How can I strip it out? Everything I try just stops there since it thinks it's the end of the file. I thought for sure there was a special variable that controlled EOF (like $/ for end of line) but I can't seem to find it.

Comment on Weird Character in File Makes Perl Think it's EOF

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Re: Weird Character in File Makes Perl Think it's EOF by Fletch (Bishop) on Oct 15, 2008 at 21:07 UTC
Sounds like someone's on win32 and trying to read a binary file in text mode. A judicious application of binmode is probably called for. The cake is a lie. The cake is a lie. The cake is a lie.	[reply]
Re^2: Weird Character in File Makes Perl Think it's EOF by Narveson (Chaplain) on Oct 16, 2008 at 04:19 UTC
Yes, we had the exact same problem where I work, and `binmode` solved it.	[reply] [d/l]
Re: Weird Character in File Makes Perl Think it's EOF by wol (Hermit) on Oct 16, 2008 at 12:14 UTC
It sounds like binmode would enable you to read past byte value 26, but then you lose the handling of the platform dependent bytes indicating end-of-line. This is only an issue if your file is supposed to be treated a text file with new-lines in it. The existence of a byte that doesn't usually appear in text files suggests that you're processing a binary file anyway, but can you confirm whether this is the case? -- .sig : File not found.	[reply]
Re: Weird Character in File Makes Perl Think it's EOF by CountZero (Bishop) on Oct 16, 2008 at 08:06 UTC
I've got some files that I'm trying to parse Can you show us your code for reading these files? As there are many ways to read a file, it is impossible to help you debug your program if we do not know what is in your program. CountZero A program should be light and agile, its subroutines connected like a string of pearls. The spirit and intent of the program should be retained throughout. There should be neither too little or too much, neither needless loops nor useless variables, neither lack of structure nor overwhelming rigidity." - The Tao of Programming, 4.1 - Geoffrey James	[reply]
Re: Weird Character in File Makes Perl Think it's EOF by ikegami (Patriarch) on Oct 19, 2008 at 21:13 UTC
Perl hasn't behaved that way for 6.5 years. >perl -e"print qq{abc\n\cZdef\n}" \| c:\progs\perl560\bin\perl -e"while + (<>) { chomp; print qq{[$_]\n} }" [abc] >perl -e"print qq{abc\n\cZdef\n}" \| c:\progs\perl561\bin\perl -e"while + (<>) { chomp; print qq{[$_]\n} }" [abc] >perl -e"print qq{abc\n\cZdef\n}" \| c:\progs\perl580\bin\perl -e"while + (<>) { chomp; print qq{[$_]\n} }" [abc] [→def] >perl -e"print qq{abc\n\cZdef\n}" \| c:\progs\perl588\bin\perl -e"while + (<>) { chomp; print qq{[$_]\n} }" [abc] [→def] >perl -e"print qq{abc\n\cZdef\n}" \| c:\progs\perl5100\bin\perl -e"whil +e (<>) { chomp; print qq{[$_]\n} }" [abc] [→def] [download] Time to upgrade! 5.8.0 is when PerlIO started being used (by ActiveState, at least). Under PerlIO, files are read in "as binary", then they are "converted to text" by the `crlf` layer if present. The `crlf` layer doesn't treat chr(26) specially like the old library did. Note: `→` represents character 26.	[reply] [d/l] [select]
Re: Weird Character in File Makes Perl Think it's EOF by periapt (Hermit) on Oct 17, 2008 at 20:32 UTC
You could certainly read the file in using binmode but, as wol noted, you do loose end-of-line handling. Depending on what is happening with your file before the parsing stage, you may want to try preprocessing it before the parse step. Assuming that your file should only have word characters in it (as defined by \w = [a-zA-Z0-9_]), you could try this one-liner `perl -i.orig -p -e "s/\W+/?/g;" <yourfile>` [download] This will rename the original file <yourfile>.orig and change every occurance of a non-word character to a question mark. I am assuming here that you want to retain the relative location of the offending byte. If you don't, simply write s/\W+// instead of s/\W+/?/. If you wanted to write the output to STDOUT say before passing the data to another process you can omit the -i.orig flag Of course, you could do it with sed or gawk but this is PerlMonks ;o). PJ use strict; use warnings; use diagnostics;	[reply] [d/l]
Re^2: Weird Character in File Makes Perl Think it's EOF by Jim (Curate) on Oct 19, 2008 at 20:40 UTC
My pre-processing suggestion would be to use tr: `tr -d "\032" < infile > outfile` ...or... `tr "\032" " " < infile > outfile` If you use Gawk, you have to set its BINMODE. Using ActivePerl for Windows, I've never had to use binmode to handle nasty ASCII control characters like NUL (0x00) and SUB (0x1A). It seems to read and write them in text mode just fine. `D:\>perl -e "print qq{\x00\x1A\nfoo\nbar\x1A\x00\n}" foo bar D:\>perl -e "print qq{\x00\x1A\nfoo\nbar\x1A\x00\n}" \| perl -ne "print if m/foo/" foo D:\>` [download] Jim	[reply] [d/l] [select]

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