Bash while 循环完成 < $1
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Bash while loop with done < $1
提问by themightyscot
I'm a bit confused by the done < $1notation.
我对done < $1符号有点困惑。
I'm trying to write a program "sumnums" that reads in a file called "nums" that has a couple rows of numbers. Then it should print out the rows of the numbers followed by a sum of all the numbers.
我正在尝试编写一个程序“sumnums”，该程序读取一个名为“nums”的文件，该文件包含几行数字。然后它应该打印出数字的行，然后是所有数字的总和。
Currently I have:
目前我有：
#!/bin/bash
sum=0;
while read myline
do
echo "Before for; Current line: \"$myline\""
done
for i in $myline; do
sum=$(expr $sum + $i)
done <
echo "Total sum is: $sum"
and it outputs the list of the numbers from nums correctly then says
./sumnums: line 10: $1: ambiguous redirect, then outputs Total sum is: 0.
它从 nums 正确./sumnums: line 10: $1: ambiguous redirect输出数字列表，然后说
，然后输出Total sum is: 0.
So somehow it isn't adding. How do I rearrange these lines to fix the program and get rid of the "ambiguous redirect"?
所以不知何故它没有添加。如何重新排列这些行以修复程序并摆脱“模糊重定向”？
回答by Charles Duffy
Assuming your filename is in $1(that is, that your script was called with ./yourscript nums):
假设您的文件名在$1（也就是说，您的脚本是用 调用的./yourscript nums）：
#!/bin/bash
[[ ]] || set -- nums ## use if already set; otherwise, override with "nums"
sum=0
while read -r i; do ## read from stdin (which is redirected by < for this loop)
sum=$(( sum + i )) ## ...treat what we read as a number, and add it to our sum
done <"" ## with stdin reading from for this loop
echo "Total sum is: $sum"
If $1doesn't contain your filename, then use something that doescontain your filename in its place, or just hardcode the actual filename itself.
如果$1不包含您的文件名，然后使用一些不包含您的文件名在其位，或只是硬编码的实际文件名本身。
Notes:
笔记：
<"$1"is applied to awhile readloop. This is essential, becausereadis (in this context) the command that actually consumes content from the file. It canmake sense to redirect stdin to aforloop, but only if something inside that loop is reading from stdin.$(( ))is modern POSIX sh arithmetic syntax.expris legacy syntax; don't use it.
<"$1"应用于while read循环。这是必不可少的，因为read（在这种情况下）是实际使用文件内容的命令。它可以是有意义的重定向标准输入到一个for循环，但只有在该循环里面的东西是从标准输入读取。$(( ))是现代 POSIX sh 算术语法。expr是遗留语法；不要使用它。
回答by karakfa
awkto the rescue!
awk来救援！
awk '{for(i=1;i<=NF;i++) sum+=$i} END{print "Total sum is: " sum}' file
bashis not the right tool for this task.
bash不是执行此任务的正确工具。
