[SOLVED] Bash String Handling

GPGAgent · 02-04-2023, 05:30 PM

Hi All, yet again I cannot get string handling in bash into my head, I don't do enough of itso here goes:

Quote:

720x480 | crop=656:480:22:32 : MyMovie.mp4

I want to get the last two crop values, 22 and 32 into variables to check.

If more than 30 then I'll report it via echo

MadeInGermany · 02-04-2023, 07:54 PM

You can split it via a read command.

Code:

IFS=":" read a b c d e <<< "720x480 | crop=656:480:22:32 : MyMovie.mp4"
echo "$c" "$d"

Or like this

Code:

[[ "720x480 | crop=656:480:22:32 : MyMovie.mp4" =~ ^[^:]*:[^:]*:([^:]*):([^:\ ]*) ]]
echo "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}"

syg00 · 02-04-2023, 09:02 PM

regex. Allows you to also easily check you are testing the correct record.

Lot easier with bash these days than it used to be.

pan64 · 02-05-2023, 04:15 AM

or you can use arrays, if you wish:

Code:

var="720x480 | crop=656:480:22:32 : MyMovie.mp4"
var2=( ${var//:/ } )
echo ${var2[3]}  # 480
echo ${var2[4]}  # 22

GPGAgent · 02-05-2023, 09:06 AM

Thank you everybody, that's brilliant - I was thinking awk was a possible solution, actually it probably is.

I could easily do this in SQL but that's becasue I've been using it for 30+ years!

GPGAgent · 02-05-2023, 09:43 AM

Quote:

Originally Posted by MadeInGermany

You can split it via a read command.

Code:

[[ "720x480 | crop=656:480:22:32 : MyMovie.mp4" =~ ^[^:]*:[^:]*:([^:]*):([^:\ ]*) ]]
echo "${BASH_REMATCH[1]}" "${BASH_REMATCH[2]}"

This worked just fine - thanks

But could you explain the mask and why its 1 and 2 in the BASH_REMATCH array

MadeInGermany · 02-05-2023, 10:40 AM

man bash

Quote:

...
Substrings matched by parenthesized subexpressions within the regular expression are saved in the array variable BASH_REMATCH. The element of BASH_REMATCH with index 0 is the portion of the string matching the entire regular expression. The element of BASH_REMATCH with index n is the portion of the string matching the nth parenthesized subexpression.
...

The RE must match, then the 1st (capture group) lands in ${BASH_REMATCH[1]} the 2nd in ${BASH_REMATCH[2]} etc. This is in tune with sed and awk where capture groups are referred as \1 \2 etc.
Also ${BASH_REMATCH[0]} is the total matching portion, like grep -o would report it.

GPGAgent · 02-05-2023, 05:23 PM

Quote:

Originally Posted by MadeInGermany

man bash

The RE must match, then the 1st (capture group) lands in ${BASH_REMATCH[1]} the 2nd in ${BASH_REMATCH[2]} etc. This is in tune with sed and awk where capture groups are referred as \1 \2 etc.
Also ${BASH_REMATCH[0]} is the total matching portion, like grep -o would report it.

Thanks, that helps loads

chrism01 · 02-05-2023, 10:45 PM

Just for fun

Code:

v1=echo ' 720x480 | crop=656:480:22:32 : MyMovie.mp4 '|cut -d':' -f3
v2=echo ' 720x480 | crop=656:480:22:32 : MyMovie.mp4 '|cut -d':' -f4