在 Bash 中循环遍历文件的内容

问题描述

如何使用 Bash 遍历文本文件的每一行?

How do I iterate through each line of a text file with Bash?

使用这个脚本:

echo "Start!"
for p in (peptides.txt)
do
    echo "${p}"
done

我在屏幕上看到这个输出:

I get this output on the screen:

Start!
./runPep.sh: line 3: syntax error near unexpected token `('
./runPep.sh: line 3: `for p in (peptides.txt)'

(后来我想用 $p 做一些更复杂的事情，而不仅仅是输出到屏幕.)

(Later I want to do something more complicated with $p than just output to the screen.)

环境变量SHELL是(来自env):

The environment variable SHELL is (from env):

SHELL=/bin/bash

/bin/bash --version 输出:

GNU bash, version 3.1.17(1)-release (x86_64-suse-linux-gnu)
Copyright (C) 2005 Free Software Foundation, Inc.

cat/proc/version 输出:

Linux version 2.6.18.2-34-default (geeko@buildhost) (gcc version 4.1.2 20061115 (prerelease) (SUSE Linux)) #1 SMP Mon Nov 27 11:46:27 UTC 2006

peptides.txt 文件包含:

The file peptides.txt contains:

RKEKNVQ
IPKKLLQK
QYFHQLEKMNVK
IPKKLLQK
GDLSTALEVAIDCYEK
QYFHQLEKMNVKIPENIYR
RKEKNVQ
VLAKHGKLQDAIN
ILGFMK
LEDVALQILL

推荐答案

一种方法是:

while read p; do
  echo "$p"
done <peptides.txt

正如评论中所指出的，这具有修剪前导空格、解释反斜杠序列以及在缺少终止换行符的情况下跳过最后一行的副作用.如果存在这些问题，您可以这样做:

As pointed out in the comments, this has the side effects of trimming leading whitespace, interpreting backslash sequences, and skipping the last line if it's missing a terminating linefeed. If these are concerns, you can do:

while IFS="" read -r p || [ -n "$p" ]
do
  printf '%s
' "$p"
done < peptides.txt

例外，如果 循环体可能从标准输入读取，您可以使用不同的文件描述符打开文件:

---

Exceptionally, if the loop body may read from standard input, you can open the file using a different file descriptor:

while read -u 10 p; do
  ...
done 10<peptides.txt

这里，10 只是一个任意数字(不同于 0、1、2).

Here, 10 is just an arbitrary number (different from 0, 1, 2).

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