perl doesn't recogize alias?

[Jianping Wu]

Hi, I am confused by the following problem:

On bash shell, I did:
alias gcc='grep'

Then I wrote a perl script with only one line:
`gcc -v`;

On bash shell, if I type "gcc -v", I got:
Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.

This is correct because gcc is aliased to grep.
But when I run the perl script, I got:
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --disable-libunwind-exceptions --with-system-zlib
--enable-__cxa_atexit --host=i386-redhat-linux
Thread model: posix
gcc version 3.3.3 20040412 (Red Hat Linux 3.3.3-7)

How come Perl doesn't recognize the aliasing?

Thanks for your help!

Jianping

 

[John Bokma]

Hi, I am confused by the following problem:

On bash shell, I did:
alias gcc='grep'

Then I wrote a perl script with only one line:
`gcc -v`;

On bash shell, if I type "gcc -v", I got:
Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.

This is correct because gcc is aliased to grep.
But when I run the perl script, I got:
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --disable-libunwind-exceptions --with-system-zlib
--enable-__cxa_atexit --host=i386-redhat-linux
Thread model: posix
gcc version 3.3.3 20040412 (Red Hat Linux 3.3.3-7)

How come Perl doesn't recognize the aliasing?

Quick guess: ` ` runs in it's own shell, e.g. if you open up another xterm
/ shell, and type gcc -v you get the same message.

 

[Chris Mattern]

Hi, I am confused by the following problem:

On bash shell, I did:
alias gcc='grep'

Then I wrote a perl script with only one line:
`gcc -v`;

Perl has a rule about how it handles backticks (and similar calling
of external programs). If it has shell metacharacters in it, it
passes the string to /bin/sh. If it doesn't, it passes the string
to exec(). Your example gets passed to exec(), so no shell aliases
for you!

On bash shell, if I type "gcc -v", I got:
Usage: grep [OPTION]... PATTERN [FILE]...
Try `grep --help' for more information.

This is correct because gcc is aliased to grep.
But when I run the perl script, I got:
Configured with: ../configure --prefix=/usr --mandir=/usr/share/man
--infodir=/usr/share/info --enable-shared --enable-threads=posix
--disable-checking --disable-libunwind-exceptions --with-system-zlib
--enable-__cxa_atexit --host=i386-redhat-linux
Thread model: posix
gcc version 3.3.3 20040412 (Red Hat Linux 3.3.3-7)

How come Perl doesn't recognize the aliasing?

Because it doesn't pass it to the shell.

Thanks for your help!

Jianping

--
Christopher Mattern

"Which one you figure tracked us?"
"The ugly one, sir."
"...Could you be more specific?"

 

[Keith Keller]

Which is the correct output. perl -v shows the version.

Small nitpick: the above is the output for gcc -v, not perl -v (or
perl -V).

--keith

 

[Axel]

Perl has a rule about how it handles backticks (and similar calling
of external programs). If it has shell metacharacters in it, it
passes the string to /bin/sh. If it doesn't, it passes the string
to exec(). Your example gets passed to exec(), so no shell aliases
for you!

Even using shell metacharacters would not help since the alias would not
be inherited.

I suppose you could place the alias in a startup file, remembering
that the behaviour of bash in reading startup files differs according
to whether it is invoked by the name 'sh' or 'bash'.

Axel

 

[Chris Mattern]

Even using shell metacharacters would not help since the alias would not
be inherited.

I suppose you could place the alias in a startup file, remembering
that the behaviour of bash in reading startup files differs according
to whether it is invoked by the name 'sh' or 'bash'.

And that's on Linux. On, say, Solaris, where /bin/sh is an honest-to-
Ritchie real Borune shell, you can't even get that, because you've
got no aliases, period.

Axel

--
Christopher Mattern

"Which one you figure tracked us?"
"The ugly one, sir."
"...Could you be more specific?"

 

[Joe Smith]

Hi, I am confused by the following problem:

On bash shell, I did:
alias gcc='grep'

That command affects the current bash shell only.
It affects how command lines in the current shell
are interpreted. You should not expect anything
else to see the alias. Perl won't see it, and
neither will any programs invoked by perl.