On Sat, 4 Jan 2003 [EMAIL PROTECTED] wrote:
> Hi Lawson!
>
> On Sat, 04 Jan 2003, [EMAIL PROTECTED] wrote:
>
> > This also seems to work:
> >
> > find -name 'Makefile'|xargs -i perl -pi -e 's/-Werror//g' {}
>
> First off thank you very much! It worked fine.
> But now I still want to understand it ;)
>
> What I dont understand is the:
>
> 1) "-i perl" option
> man page says:
> --replace[=replace-str], -i[replace-str]
> Replace occurences of replace-str in the initial
> arguments with names read from standard input.
> Also, unquoted blanks do not terminate arguments.
> If replace-str is omitted, it defaults to "{}"
> (like for `find -exec'). Implies -x and -l 1.
the first -i is an option to xargs, so it will run the command
perl -pi -e 's/-Werror//g' {}
once for each filename find found, with the filename substituted for the
{}
I should have said find -type f -name ... in case you had any
directories named Makefile.
>
> As I understand this it calls perl and executes the regexp on a file.
> The explanation of the -i option in man page of xargs and that it
> calls perl doesnt fit together in my understanding.
calls perl once for each file.
>
> 2) "-pi" option
> "-p" runs the "program" first through the C preprocessor, right? But
> what for?
No, that is -P
-p couses perl to execute the command on each line of each named file.
I'll attach an excerpt from man perlrun that describes it.
>
> "-i" means that the file is edited in-place? What does that mean?
The changed file replaces the original file.
>
> 3) What is the {} for?
>
The default --replace-string for xargs.
>
> Thank you very much,
> Axel
>
--
---oops---
-p causes Perl to assume the following loop around your
program, which makes it iterate over filename argu-
ments somewhat like sed:
LINE:
while (<>) {
... # your program goes here
} continue {
print or die "-p destination: $!\n";
}
If a file named by an argument cannot be opened for
some reason, Perl warns you about it, and moves on to
the next file. Note that the lines are printed auto-
matically. An error occurring during printing is
treated as fatal. To suppress printing use the -n
switch. A -p overrides a -n switch.
`BEGIN' and `END' blocks may be used to capture con-
trol before or after the implicit loop, just as in
awk.
-P causes your program to be run through the C prepro-
cessor before compilation by Perl. (Because both
comments and cpp directives begin with the # charac-
ter, you should avoid starting comments with any
words recognized by the C preprocessor such as "if",
