[SOLVED] mv --dereference

metaed · 03-22-2023, 05:08 PM

Contrary to the Bash FAQ, I value the visual difference of `` for command substitution, $ for symbol substitution. I can tell at a glance when I'm dereferencing a shell variable and when I'm creating a subshell.

I admit this is due to having a legacy brain. Legacy brains that still run legacy shell are inevitably going to write legacy shell scripts. And backtick command substitution is the go-to for true compatibility with legacy brains (and shells).

jrosevear · 03-22-2023, 05:40 PM

Quote:

Originally Posted by boughtonp

It's a bug in the script - it incorrectly splits quoted arguments.

Code:

$ tail example{1,2}.sh
==> example1.sh <==
#!/bin/sh
file $*
==> example2.sh <==
#!/bin/sh
file "$@"

$ ./example1.sh test_file1 'test file2'
test_file1: ASCII text
test:       cannot open `test' (No such file or directory)
file2:      cannot open `file2' (No such file or directory)

$ ./example2.sh test_file1 'test file2'
test_file1: ASCII text
test file2: ASCII text

Hello boughtonp,

Thank you for your reply.

I tried your example above and it confirmed my understanding. I agree with you about the behavior of $* and "$@". I think this is an important bit of knowledge and very much a worthwhile thing to talk about.

I suppose that it is, in fact, a bug. Especially so if it bites you.

-Joe

Llyich · 03-22-2023, 07:32 PM

Hello jrosevear,
Thank you for your response and for your interest in the links.

Test
Before ordering:
Physical source
/media/serv/ja05/rm/source.mkv
Link:
/home/serv/Link/00/source.mkv -> /media/serv/ja05/rm/source.mkv)
Purpose:
/media/serv/ja05/000

Command (jrosevear response):

Quote:

mv `readlink -f "/home/serv/Lien/00/source.mkv"` "/media/serv/ja05/000"

After the command:
Physical source
/media/serv/ja05/rm/source.mkv
Link:
/home/serv/Link/00/source.mkv -> /media/serv/ja05/rm/source.mkv
Purpose:
/media/serv/ja05/000/source.mkv

Additionals commands:
rm `readlink -f "/home/serv/Lien/00/source.mkv"`
rm /home/serv/Link/00/source.mkv

After the additionals commands:
Physical source
/media/serv/ja05/rm/
Link:
/home/serv/Link/00/
Purpose:
/media/serv/ja05/000/source.mkv

This is an mv on the same ja05 hard drive, source.mkv is several Gio in size, the command was instant, instead of 10 minutes using a cp -rvL

Kind regards,
Llyich

jrosevear · 03-22-2023, 10:20 PM

Quote:

Originally Posted by Llyich

Hello jrosevear,
Thank you for your response and for your interest in the links.

Test
Before ordering:
Physical source
/media/serv/ja05/rm/source.mkv
Link:
/home/serv/Link/00/source.mkv -> /media/serv/ja05/rm/source.mkv)
Purpose:
/media/serv/ja05/000

Command (jrosevear response):

After the command:
Physical source
/media/serv/ja05/rm/source.mkv
Link:
/home/serv/Link/00/source.mkv -> /media/serv/ja05/rm/source.mkv
Purpose:
/media/serv/ja05/000/source.mkv

Additionals commands:
rm `readlink -f "/home/serv/Lien/00/source.mkv"`
rm /home/serv/Link/00/source.mkv

After the additionals commands:
Physical source
/media/serv/ja05/rm/
Link:
/home/serv/Link/00/
Purpose:
/media/serv/ja05/000/source.mkv

This is an mv on the same ja05 hard drive, source.mkv is several Gio in size, the command was instant, instead of 10 minutes using a cp -rvL

Kind regards,
Llyich

Hello Llyich,

Thank you for your reply.

I'm afraid I don't understand. Would you like to send me an email in your native language? My email is Mail@JoesLife.org

-Joe

pan64 · 03-23-2023, 03:24 AM

Quote:

Originally Posted by boughtonp

I've no idea why Pan64 wrote "I guess you wanted to use bash, not sh (see your shebang)" - there's no Bash-specific syntax there, so no benefit in requiring Bash.

If it's intentionally /bin/sh, it's perfectly fine. I just wasn't sure, and using sh instead of bash (unintentionally) might cause surprises.