Removing leading and trailing white spaces as well as leading zeroes

You may use this regex in perl:

s/^\h*0*(?=\d)|\h+$

RegEx Details:

• \h matches a horizontal whitespace
• ^\h*0*(?=\d): At the start it will match 0 or more leading whitespaces followed by 0 or more leading zeroes as long as there is at least one digit ahead
• | OR
• \h+$: At the end it will match 1+ horizontal whitespaces

Examples:

perl -pe 's/^\h*0+(?=\d)|\h+$//g' <<< ' 001 '
1

perl -pe 's/^\h*0+(?=\d)|\h+$//g' <<< ' 000 '
0

perl -pe 's/^\h*0+(?=\d)|\h+$//g' <<< '     0000000123     '
123

perl -pe 's/^\h*0*(?=\d)|\h+$//g' <<< ' 123   '
123

You may use

s/^[\s0]+|\s+$//g

Or, for a corner case like ' 0000 ' where you would still like to keep one zero:

s/^(?:\s*(0)+\s*$|[\s0]+)|\s+$/$1/g

See the regex demo #1 and regex demo #2.

Details

• ^[\s0]+ - matches one or more zeros or whitespace at the start of the string
• ^(?:\s*(0)+\s*$|[\s0]+) - matches
  • ^ - start of string
  • (?:\s*(0)+\s*$|[\s0]+) - either of
    • \s*(0)+\s*$ - 0+ whitespaces, 1 or more zeros each time captured into Group 1, and then 0+ whitespaces till end of string
    • |- or
    • [\s0]+ - 1 or more whitespaces or zeros
• | - or
• \s+$ - matches one or more whitespace chars at the end of string.