用一行shell命令做累加操作

本文最后更新于2014年11月14日,已超过 1 年没有更新,如果文章内容失效,还请反馈给我,谢谢!

在Stackoverflow上看到的一则问答,之前有收集过一些,在里面都包括了,还扩充了不少,值得学习,就此记录如下(实例):

# cat num.txt
1
2
3
4
5
6
7
8
9
10

# awk '{s+=$1} END {print s}' num.txt
55
# paste -s -d+ num.txt | bc
55
# cat num.txt | python -c "import sys; print sum(int(l) for l in sys.stdin)"
55
# cat num.txt | perl -lpe '$c+=$_}{$_=$c'
55
# cat num.txt | xargs | sed -e 's/ /+/g' | bc
55
# cat num.txt | xargs
1 2 3 4 5 6 7 8 9 10

# cat num.txt | perl -MList::Util -le 'print List::Util::sum(<>)'
55
# sed 's/^/.+/' num.txt | bc | tail -1
55
# sed 's/^/.+/' num.txt | bc
1
3
6
10
15
21
28
36
45
55

最方便的还是awk啊,其次就是sed/xargs加上bc的组合了,Perl、Python什么的也不错。

1.paste命令
Using existing file:
paste -sd+ infile | bc

Using stdin:
<cmd> | paste -sd+ | bc

Edit: With some paste implementations you need to be more explicit when reading from stdin:
<cmd> | paste -sd+ - | bc

2.awk命令(效率高于上面的paste命令)
I like the chosen answer. However, it tends to be slower than awk since 2 tools are needed to do the job.

$ wc -l file
49999998 file

$ time paste -sd+ file | bc
1448700364

real    1m36.960s
user    1m24.515s
sys     0m1.772s

$ time awk '{s+=$1}END{print s}' file
1448700364

real    0m45.476s
user    0m40.756s
sys     0m0.287s

3.先cat然后tr最后管道传给bc命令
You can use bc (calculator). Assuming your file with #s is called "n":

$ cat n
1
2
3
$ (cat n | tr "\012" "+" ; echo "0") | bc
6
The tr changes all newlines to "+"; then we append 0 after the last plus, then we pipe the expression (1+2+3+0) to the calculator

4.Perl方法
Or, if you are OK with using awk or perl, here's a Perl one-liner:

$perl -nle '$sum += $_ } END { print $sum' n
6

5.将循环写在单行
while read -r num; do ((sum += num)); done < inputfile; echo $sum

 

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