change character with "/" in a file

[support_billa]

hello,

what is the best way to change characters with "/" ( like a HPUX Volume Group ) in a file and also preserve the file permission, file owner ....

sed, awk or perl ?

i have some examples:

fs_act_vg=/dev/vgact

fs_new_vg=/dev/vgnew

SED:

sed "s|^/dev/${fs_act_vg}|/dev/${fs_new_vg}|g" file > file_new

cp file_new file

AWK:

but no finished ...
awk -v fs_act_vg="/dev/${fs_act_vg}" -v fs_new_vg="/dev/${fs_new_vg}" '$0 ~ fs_act_vg {print sub( $0,fs_act_vg,fs_new_vg) }' file > file_new
cp file_new file

PERL
perl -i.old -p -e "s/\/dev\/${fs_act_vg}/\/dev\/${fs_new_vg}/ if /\/dev\/${fs_act_vg}/" file

regards

[James R. Ferguson]

Hi:

The best way?  Define "best" --- shortest number of characters?  Readability (assuming you know each language)?  Smallest number of processes?   Smallest process footprint?  Speed?

By the way, you can golf your perl script to eliminate the toothpicks (escaped forward slash characters) by changing the delimiter from '/' to balanced pairs of angle, round, square or curly brackets.

Regards!

...JRF...

[support_billa]

The best way?  Define "best" --- shortest number of characters?  Readability (assuming you know each language)?

i know very well "sed", "awk" but when i want to change a content in a file , i always must work with a temporary file ?  a colleague ( he didn't work in our company) change "sed" to "perl" because we had some problems with "sed" and temporary files. so i think "perl" one liner are a good alternative ?

improvment : ( a better way for "if" i didn't find )

perl -i.old -p -e "s |/dev/${fs_act_vg}|/dev/${fs_new_vg}| if /\/dev\/${fs_act_vg}/ "

regards

regards

[James R. Ferguson · Accepted solution]

Hi (again):

The GNU 'sed' offers in-place editing akin to Perl.  The use of 'awk' wold require a temporary file.

perl -i.old -p -e "s |/dev/${fs_act_vg}|/dev/${fs_new_vg}| if /\/dev\/${fs_act_vg}/ "

...does not need the 'if' condition.  The substitution will occur only if there is a match of the first operand, so:

perl -pi.old -e "s|/dev/${fs_act_vg}|/dev/${fs_new_vg}|"

Regards!

...JRF...