如何在Bash脚本中使用带变量的Awk命令删除文件特定内容

Let's break down what's going wrong with your command and how to adjust it to delete the target text block using a variable.

Key Issues in Your Original Command #

1. Shell variables aren't automatically available in Awk: When you run P="Part 2" awk ..., the P variable is set in the shell environment, but Awk doesn't pick it up unless explicitly told to.
2. Incorrect variable interpolation in regex: Using $P inside a regex literal (/.../) is invalid in Awk. The $ symbol in Awk refers to field numbers (like $1 for the first field), not variable substitution.

Corrected Awk Commands #

Method 1: Pass the variable to Awk with -v

This is the most straightforward approach. Use the -v flag to export the shell variable into Awk, then build your regex pattern using string concatenation with the ~ operator:

P="Part 2"
awk -v part="$P" '
$0 ~ "^[#]+(" part " start)[#]+" { f=1 }
f && $0 ~ "^[#]+(" part " end)[#]+" { f=0; next }
!f' test.txt

Method 2: Access the environment variable directly in Awk

If you prefer to keep the variable in the shell environment, use Awk's ENVIRON array to retrieve its value:

P="Part 2" awk '
$0 ~ "^[#]+(" ENVIRON["P"] " start)[#]+" { f=1 }
f && $0 ~ "^[#]+(" ENVIRON["P"] " end)[#]+" { f=0; next }
!f' test.txt

How This Works #

• The -v part="$P" flag creates an Awk variable part with the value of your shell's P variable.
• The ~ operator checks if the current line ($0) matches the constructed regex pattern. We build the pattern by concatenating the part variable with the fixed strings " start" and " end", wrapped in the matching # characters.
• The f flag works exactly as in your original command: it toggles on when we hit the start of the target block, and toggles off (skipping the end line) when we hit the block's end. Lines are only printed when f is false.

Example Output #

Running either corrected command will produce the desired result:

#######################Part 1 start######################
text
#######################Part 1 end#######################
#######################Part 3 start#####################
text
#######################Part 3 end#######################

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