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awk FS or -F 的使用

news 2026/6/5 8:25:21

ls *.txt

得到如何结果：

Chapter_10.Programming_Problems_Using_File.7_pages.txt
Chapter_11.Array_Index,_Security,_and_Trends.6_pages.txt
Chapter_12.Version_Control.14_pages.txt
Chapter_13.Concept.11_pages.txt
Chapter_14.Recursive_C_Functions.15_pages.txt
Chapter_15.Integer_Partition.10_pages.txt
Chapter_16.Programming_Problems_Using_Recursion.18_pages.txt
Chapter_17.Programmer-Defined_Data_Types.26_pages.txt
Chapter_18.Programming_Problems_Using_Structure.16_pages.txt
Chapter_19.Linked_Lists.9_pages.txt
Chapter_1.Program_Execution.5_pages.txt
Chapter_20.Programming_Problems_Using_Linked_List.9_pages.txt
Chapter_21.Binary_Search_Trees.13_pages.txt
Chapter_22.Parallel_Programming_Using_Threads.21_pages.txt
Chapter_23.Unit_Test.22_pages.txt
Chapter_24.Find_the_Exit_of_a_Maze.9_pages.txt
Chapter_25.Sudoku.20_pages.txt
Chapter_26.Image_Processing.14_pages.txt
Chapter_27.Huffman_Compression.27_pages.txt
Chapter_2.Stack_Memory.16_pages.txt
Chapter_3.Prevent,_Detect,_and_Remove_Bugs.8_pages.txt
Chapter_4.Pointers.22_pages.txt
Chapter_5.Writing_and_Testing_Programs.15_pages.txt
Chapter_6.Strings.8_pages.txt
Chapter_7.Heap_Memory.11_pages.txt
Chapter_8.Programming_Problems_Using_Heap_Memory.13_pages.txt
Chapter_9.Reading_and_Writing_Files.9_pages.txt

问题是，如何sort，保证按chapter1,2,3这样来排序：

可以使用awk，把1，2，3，4...给单独提取出来，放在文档的头部，再使用sort -n排序：

如何提取出1，2，3，4呢？awk的FS提供了方法：

$ ls *.txt | awk -F"_\|." {print $2}

如何这样，运行后，会发现结果不对。

看gemini的分析的：

The main issue with your command is how the shell and awk interpret special characters, specifically the pipe (|) and the backslash (\). Because you haven't quoted the field separator argument, the shell is likely trying to treat | as a pipe for the entire command rather than a character for awk to use.

Here is a breakdown of what’s going wrong and how to fix it.

1. Missing Quotes

In your original code, -F"_\|.", the shell sees the | and gets confused. To awk, the field separator -F should be wrapped in single quotes so the shell passes the string literally to the awk engine.

2. The Regex Logic

Inside awk, the -F flag defines a Regular Expression.

If you want to split by an underscore OR a literal dot, you need to escape the dot (because . in regex means "any character").
The pipe | is the "OR" operator in regex.

3. Escape Sequences

To represent a literal pipe or a literal dot in an awk regex string, you often need a double backslash because of how the string is parsed. However, using a bracket expression [_.] is much cleaner and more reliable.

The Corrected Solutions

Option A: The "Bracket" Approach (Recommended)

This is the cleanest way to say "split at either an underscore or a dot."

Bash 

ls *.txt | awk -F '[_.]' '{print $2}'

Option B: The "Regex OR" Approach

If you prefer the "OR" logic, you must quote the separator and escape the dot.

Bash 

ls *.txt | awk -F '_|\\.' '{print $2}'

Important Note on `ls`

While this fixes your awk syntax, parsing the output of ls is generally considered "fragile" in scripting because it can break if filenames contain spaces or newlines. If you are doing this inside a script, a for loop is usually safer:

Bash 

for file in *.txt; doecho "$file" | awk -F '[_.]' '{print $2}'
done

Quick Tip: If your filename is data_v1.txt, $2 will give you v1. If your filename is report_2023_final.txt, $2 will give you 2023. Make sure the field index corresponds to the specific part of the name you're hunting for!

最终的版本：

$ ls *.txt | awk -F'[_.]' ' {print $2 " " $0}' | sort -n

1 Chapter_1.Program_Execution.5_pages.txt
2 Chapter_2.Stack_Memory.16_pages.txt
3 Chapter_3.Prevent,_Detect,_and_Remove_Bugs.8_pages.txt
4 Chapter_4.Pointers.22_pages.txt
5 Chapter_5.Writing_and_Testing_Programs.15_pages.txt
6 Chapter_6.Strings.8_pages.txt
7 Chapter_7.Heap_Memory.11_pages.txt
8 Chapter_8.Programming_Problems_Using_Heap_Memory.13_pages.txt
9 Chapter_9.Reading_and_Writing_Files.9_pages.txt
10 Chapter_10.Programming_Problems_Using_File.7_pages.txt
11 Chapter_11.Array_Index,_Security,_and_Trends.6_pages.txt
12 Chapter_12.Version_Control.14_pages.txt
13 Chapter_13.Concept.11_pages.txt
14 Chapter_14.Recursive_C_Functions.15_pages.txt
15 Chapter_15.Integer_Partition.10_pages.txt
16 Chapter_16.Programming_Problems_Using_Recursion.18_pages.txt
17 Chapter_17.Programmer-Defined_Data_Types.26_pages.txt
18 Chapter_18.Programming_Problems_Using_Structure.16_pages.txt
19 Chapter_19.Linked_Lists.9_pages.txt
20 Chapter_20.Programming_Problems_Using_Linked_List.9_pages.txt
21 Chapter_21.Binary_Search_Trees.13_pages.txt
22 Chapter_22.Parallel_Programming_Using_Threads.21_pages.txt
23 Chapter_23.Unit_Test.22_pages.txt
24 Chapter_24.Find_the_Exit_of_a_Maze.9_pages.txt
25 Chapter_25.Sudoku.20_pages.txt
26 Chapter_26.Image_Processing.14_pages.txt
27 Chapter_27.Huffman_Compression.27_pages.txt

上面的命令再添加 awk '{print $2}'

$ ls *.txt | awk -F'[_.]' ' {print $2 " " $0}' | sort -n | awk '{print $2}'

Chapter_1.Program_Execution.5_pages.txt
Chapter_2.Stack_Memory.16_pages.txt
Chapter_3.Prevent,_Detect,_and_Remove_Bugs.8_pages.txt
Chapter_4.Pointers.22_pages.txt
Chapter_5.Writing_and_Testing_Programs.15_pages.txt
Chapter_6.Strings.8_pages.txt
Chapter_7.Heap_Memory.11_pages.txt
Chapter_8.Programming_Problems_Using_Heap_Memory.13_pages.txt
Chapter_9.Reading_and_Writing_Files.9_pages.txt
Chapter_10.Programming_Problems_Using_File.7_pages.txt
Chapter_11.Array_Index,_Security,_and_Trends.6_pages.txt
Chapter_12.Version_Control.14_pages.txt
Chapter_13.Concept.11_pages.txt
Chapter_14.Recursive_C_Functions.15_pages.txt
Chapter_15.Integer_Partition.10_pages.txt
Chapter_16.Programming_Problems_Using_Recursion.18_pages.txt
Chapter_17.Programmer-Defined_Data_Types.26_pages.txt
Chapter_18.Programming_Problems_Using_Structure.16_pages.txt
Chapter_19.Linked_Lists.9_pages.txt
Chapter_20.Programming_Problems_Using_Linked_List.9_pages.txt
Chapter_21.Binary_Search_Trees.13_pages.txt
Chapter_22.Parallel_Programming_Using_Threads.21_pages.txt
Chapter_23.Unit_Test.22_pages.txt
Chapter_24.Find_the_Exit_of_a_Maze.9_pages.txt
Chapter_25.Sudoku.20_pages.txt
Chapter_26.Image_Processing.14_pages.txt
Chapter_27.Huffman_Compression.27_pages.txt