Interesting bash behavior

Question

Why does this command (creating an empty folder, changing it, touching a file, calling ls, and then cating) display two files?

root@ubuntu:~# mkdir a ; cd a ; touch b ; ls > c ; cat c
b
c

I believe that I only need a "b".

Answer 1

When you redirect the output lsto a file c, this is a chicken and egg problem:

If cit was not created in advance, this meant that the shell would need to save the output in a buffer and (at the end) write this buffer to a file.

Since in many cases this is not the best approach (due to memory management, failure management for commands that are interrupted before completion, etc.), the file is created in advance.

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Answer 2

ls > c

c ls. touch b ( b - ). ,

mkdir t ; cd t ; ls > a ; cat a

a (, > a ls exec ).

Answer 3

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Answer 4

, ls c, , .

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