Bash script to mkdir on each line of a file that has been split by a delimiter?

问题

Trying to figure out how to iterate through a .txt file (filemappings.txt) line by line, then split each line using tab(\t) as a delimiter so that we can create the directory specified on the right of the tab (mkdir -p).

Reading filemappings.txt and then splitting each line by tab

server/ /client/app/
server/a/   /client/app/a/
server/b/   /client/app/b/

Would turn into

mkdir -p /client/app/
mkdir -p /client/app/a/
mkdir -p /client/app/b/

Would xargs be a good option? Why or why not?

回答1:

cut -f 2 filemappings.txt | tr '\n' '\0' | xargs -0 mkdir -p 

xargs -0 is great for vector operations.

回答2:

You already have an answer telling you how to use xargs. In my experience xargs is useful when you want to run a simple command on a list of arguments that are easy to retrieve. In your example, xargs will do nicelly. However, if you want to do something more complicated than run a simple command, you may want to use a while loop:

while IFS=$'\t' read -r a b
do
  mkdir -p "$b"
done <filemappings.txt

In this special case, read a b will read two arguments separated by the defined IFS and put each in a different variable. If you are a one-liner lover, you may also do:

while IFS=$'\t' read -r a b; do mkdir -p "$b"; done <filemappings.txt

In this way you may read multiple arguments to apply to any series of commands; something that xargs is not well suited to do.

Using read -r will read a line literally regardless of any backslashes in it, in case you need to read a line with backslashes.

Also note that some operating systems may allow tabs as part of a file or directory name. That would break the use of the tab as the separator of arguments.

回答3:

As others have pointed out, \t character could also be a part of the file or directory name, and the following command may fail. Assuming the question represents the true form of the input file, one can use:

  $ grep -o -P '(?<=\t).*' filemappings.txt | xargs -d'\n' mkdir -p

It uses -P perl-style regex to get words after the \t(TAB) character, then use -d'\n' which provides all relevant lines as a single input to mkdir -p.

回答4:

sed -n '/\t/{s:^.*\t\t*:mkdir -p ":;s:$:":;p}' filemappings.txt | bash

---

1. sed -n: only work with lines that contains tab (delimiter)
2. s:^.*\t\t*:mkdir -p :: change all things from line beggning to tab to mkdir -p
3. | bash: tell bash to create folders

回答5:

With GNU Parallel it looks like this:

parallel --colsep '\t' mkdir -p {2} < filemapping.txt

来源：https://stackoverflow.com/questions/48305724/bash-script-to-mkdir-on-each-line-of-a-file-that-has-been-split-by-a-delimiter