使用 bash 从文本文件中读取字符
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Read characters from a text file using bash
提问by Simon Hodgson
Does anyone know how I can read the first two characters from a file, using a bash script. The file in question is actually an I/O driver, it has no new line characters in it, and is in effect infinitely long.
有谁知道我如何使用 bash 脚本从文件中读取前两个字符。有问题的文件实际上是一个 I/O 驱动程序，其中没有换行符，并且实际上是无限长的。
回答by Vinko Vrsalovic
The readbuiltin supports the -nparameter:
将read内置支持-n参数：
$ echo "Two chars" | while read -n 2 i; do echo $i; done
Tw
o
ch
ar
s
$ cat /proc/your_driver | (read -n 2 i; echo $i;)
回答by shodanex
I think
dd if=your_file ibs=2 count=1will do the trick
我认为
dd if=your_file ibs=2 count=1会做的伎俩
Looking at it with strace shows it is effectively doing a two bytes read from the file. Here is an example reading from /dev/zero, and piped into hd to display the zero :
用 strace 查看它表明它有效地从文件中读取了两个字节。这是从 /dev/zero 读取的示例，并通过管道传输到 hd 以显示零：
dd if=/dev/zero bs=2 count=1 | hd
1+0 enregistrements lus
1+0 enregistrements écrits
2 octets (2 B) copiés, 2,8497e-05 s, 70,2 kB/s
00000000 00 00 |..|
00000002
回答by Rob Wells
G'day,
G'day,
Why not use od to get the slice that you need?
为什么不使用 od 来获取您需要的切片？
od --read-bytes=2 my_driver
Edit:You can't use head for this as the head command prints to stdout. If the first two chars are not printable, you don't see anything.
编辑：您不能为此使用 head，因为 head 命令打印到标准输出。如果前两个字符不可打印，您将看不到任何内容。
The od command has several options to format the bytes as you want.
od 命令有几个选项可以根据需要格式化字节。
回答by ghostdog74
echo "Two chars" | sed 's/../&\n/g'
