使用sed命令替换XML中<l_num>标签内数字失败，求排查原因

Let's break down what's wrong with your original sed command and fix it to meet your requirements:

Issues with the Original Command #

• Incorrect word boundaries (): The  matches word boundaries (between alphanumeric/underscore and non-word characters), but <l_num> ends with > (a non-word character) and the number starts right after it—there's no word boundary here. Same issue with the closing </l_num>: the number ends before <, which is also not a word boundary, so the trailing  doesn't work.
• Misused line anchors (^/$): You used line start (^) and line end ($) anchors, but the <l_num> tag and its content are just part of a line, not the entire line. This makes the regex fail to match anything at all.
• Unrestricted number matching: The regex [0-9]([0-9]*) matches any number (like 17, 100, etc.), not just the 0-16 range you need.
• Minor typo in closing tag: Your expected output uses </l_num>, but the command wrote </lnum> (missing the underscore)—easy fix once the matching works.

Corrected Sed Command for 0-16 Replacement #

To match only valid 0-16 values (no leading zeros for single-digit numbers) and replace them with 5, use this command:

sed -i -r 's/<l_num>(0|[1-9]|1[0-6])<\/l_num>/<l_num>5<\/l_num>/g' test.xml

Regex Breakdown: #

• (0|[1-9]|1[0-6]): This grouped pattern explicitly matches:
  • 0 (the single-digit zero)
  • [1-9] (single-digit numbers 1-9, no leading zeros)
  • 1[0-6] (two-digit numbers 10-16, covering the upper end of your range)
• We directly match the full <l_num>...</l_num> tag structure without incorrect boundaries or line anchors, ensuring we only target valid tag content.

Handling the "05" Replacement Case #

If you want to skip modifying the file entirely when the replacement value is 05 (since 05 violates the "no leading zeros for single-digit numbers" rule), wrap the sed command in a shell condition to validate the replacement value first:

REPLACE_VALUE="05"
# Check if the replacement value is valid (0-16, no leading zeros)
if [[ "$REPLACE_VALUE" =~ ^0$|^[1-9]$|^1[0-6]$ ]]; then
  sed -i -r "s/<l_num>(0|[1-9]|1[0-6])<\/l_num>/<l_num>$REPLACE_VALUE<\/l_num>/g" test.xml
else
  echo "Replacement value '$REPLACE_VALUE' is invalid (no leading zeros for single digits, must be 0-16). No changes made."
fi

This way, if you set REPLACE_VALUE to 05, the condition fails, and the file remains untouched.

内容的提问来源于stack exchange，提问作者skrowten_hermit