这个 sed 命令的含义是什么：`;/@/{h;s/test/next/g;x;G}`？

Question

sed -e 's/72;/72, next_val = 0x11111111;/;/@/{h;s/test/next/g;x;G}'
fmt_vuln.c > fmt_vuln2.c

你能告诉我是什么意思;/@/{h;s/test/next/g;x;G}吗？

Answer 1

/@/ # For pattern-space containing the character @ do the following
{
  h              # place a copy of the pattern-space into the hold-space
  s/test/next/g  # replace all instances of "test" with "next" in the pattern-space
  x              # swap the pattern-space with the hold-space
  G              # append a newline followed by contents of hold-space to the pattern-space
}

因此，对于包含 @ 的每一行，将打印模式空间的修改版本，然后是原始版本（保留空间包含未修改的版本）。

请参阅Sed 的命令摘要

Answer 2

;/@/{h;s/test/next/g;x;G}? 

/@/  search for an `@` sign
{}   for the lines where that is true do this 'block' of code
h    put the pattern match in the hold space
s/   substitute test for next everywhere in the space
g    do the previous substitution for all matches on the line
x    swap the hold with the pattern space
G    Add a new line with the contents of the hold space.