从bash中的ascii文件读取的字符串创建多个循环 [英] Creating multiple loops with string read from ascii files in bash

问题描述

我想在一个内部循环中创建一个内部循环，其中包含从bash脚本中的ascii文件读取的字符串.我有两个包含字符串列表的输入ascii文件:

I want to create an internal loop inside a loop with strings which are read from ascii files in a bash script. I have two input ascii files which contain a list of strings:

files.txt:
filename1
filename2


polls.txt:
CO
NOx
SOx

我使用了IFS，内容如下:

I used IFS and read as following :

while IFS= read -r file; do
   printf '%s\n' "$file"

    while IFS= read -r poll; do
       printf '%s\n' "$poll"
       ogrinfo $Database_maindir/$file".shp" -sql "ALTER TABLE $file ADD COLUMN $poll float"
    done < "$Database_maindir/polls.txt"

done < "$Database_maindir/files.txt"

我得到以下打印和错误:

I get the following prints and errors:

CO
CO
FAILURE:
Unable to open datasource `/home/CO.shp' with the following drivers.

它仅读取"polls.txt"字符串.

It reads only the string of "polls.txt".

正确的输出应为:

filename1
CO
ogrinfo /home/"filename1.shp" -sql "ALTER TABLE filename1 ADD COLUMN CO float"
NOx
ogrinfo /home/"filename1.shp" -sql "ALTER TABLE filename1 ADD COLUMN NOx float"
Sox
ogrinfo /home/"filename1.shp" -sql "ALTER TABLE filename1 ADD COLUMN Sox float"

filename2
CO
ogrinfo /home/"filename2.shp" -sql "ALTER TABLE filename2 ADD COLUMN CO float"
NOx
ogrinfo /home/"filename2.shp" -sql "ALTER TABLE filename2 ADD COLUMN NOx float"
Sox
ogrinfo /home/"filename2.shp" -sql "ALTER TABLE filename2 ADD COLUMN Sox float"

因此，对于每个文件(例如filename1，filename2)，我想执行COMMAND(例如ogrinfo命令，该命令将更新文件中的列，而这些列是polls.txt中列出的不同污染物.

So, for each file (e.g. filename1, filename2) I want to execute a COMMAND (e.g. an ogrinfo command which updates the columns of a file where the columns are different pollutants listed in the polls.txt.

在第一个循环中，我想从files.txt中读取字符串，并将字符串$ file保留为字符串的名称(例如filename1).在第二个循环中，我想从"polls.txt"中读取字符串，并保留字符串$ poll(例如CO).

In the first loop I want to read the strings from the files.txt and keep the string $file with the name of the string (e.g. filename1). In the second loop I want to read the strings from "polls.txt" and keep the string $poll (e.g.CO).

但是，似乎在第一个循环中，它从找到的第一个文件中读取了字符串，即"polls.txt"，因此$ file给出了字符串"CO".

However, it seems that for the first loop it reads the string from the first file it finds , meaning the "polls.txt", so $file gives the string "CO".

我如何定义第一个循环应读取第二个txt文件?

How I could define that the first loop should read the second txt file?

推荐答案

1. 使用专用文件描述符.这样，您可以100％确保每个read从正确的流中读取.而且循环内的命令也不会从流中读取.

1. Use dedicated file descriptors. That way you are 100% sure each read reads from the proper stream. And the commands inside the loop also don't read from the stream.

while IFS= read -r -u 3 file; do
   printf '%s\n' "$file"

    while IFS= read -r -u 4 poll; do
       printf '%s\n' "$poll"
       echo ogrinfo $Database_maindir/$file".shp" -sql "ALTER TABLE $file ADD COLUMN $poll float"
    done 4< "$Database_maindir/polls.txt"

done 3< "$Database_maindir/files.txt"

1. 使用不可读的脚本，该脚本首先通过将第一个文件重复第二个文件具有的行数，然后将第二个文件中的每一行重复第一个文件中的行数来将两个文件合并在一起，然后运行xargs(ideas从此处和此处)

paste <(
    awk -v nr=$(wc -l <polls.txt) \
        '{for (i = 1; i <= nr; i++) print}' files.txt
) <(
    seq $(wc -l <files.txt) |
    xargs -n1 cat polls.txt
) |
xargs -n2 sh -c 'echo ogrinfo "$1".shp -sql "ALTER TANLE $1 ADD COLUMN $2 float"' --

这篇关于从bash中的ascii文件读取的字符串创建多个循环的文章就介绍到这了，希望我们推荐的答案对大家有所帮助，也希望大家多多支持IT屋！