[Linux 常見問題] Bash - Remove the last line from a file

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Question
I have a file, foo.txt, containing the following lines:

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1. a  
2. b  
3. c  

I want a simple command that results in the contents of foo.txt being:

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1. a  
2. b  

How-To
This is by far the fastest and simplest solution, especially on big files:

// -n, --lines=[-]NUM: print the first NUM lines instead of the first 10; with the leading '-', print all but the last NUM lines of each file
# cat foo.txt
a
b
c

# head -n +2 foo.txt
a
b

# head -n -1 foo.txt
a
b

# head -n -1 foo.txt > temp.txt ; mv temp.txt foo.txt

Do not use sed for deleting lines from the top or bottom of a file -- it's very very slow if the file is large. It can still work as below:

# sed '$ d' test.txt
a
b