How to count the line number of a file? It seems an easy question for Unix guys: using wc command. Let’s see an example:
# cat test
aaaa
bbbb
cccc
# wc -l test
3 test
It displays right. But wait a minute, let’s check the wc -l option meaning:
# wc --help
......
-l, --lines print the newline counts
......
wc -l just print the newline counts, so it increases newline count as the line number. Using hexdump to see the content of test:
# hexdump -C test
00000000 61 61 61 61 0a 62 62 62 62 0a 63 63 63 63 0a |aaaa.bbbb.cccc.|
0000000f
No problem, test contains 3 newlines. But now, the question is here, how about the last line doesn’t contain newline?
Let me do the following experiment:
# echo -n "a" > test
# hexdump -C test
00000000 61 |a|
00000001
# wc -l test
0 test
Now the test file only contains 1 character, and no newline. This time, wc -l thinks there is no line in test file.
Based on the previous discussion, maybe awk is a better tool when using to count line number of file. Just one statement:
# awk 'END {print NR}' test
1
It outputs right line number.