for循环回显顺序命令行？

Question

如何在linux中使用for循环来生成以下几行？

zcat ~/tools/sample66621D.fastq | bowtie2 -a - | samtools ->sample66621D.BAM 
zcat ~/tools/sample66622D.fastq | bowtie2 -a - | samtools ->sample66622D.BAM 
zcat ~/tools/sample66623D.fastq | bowtie2 -a - | samtools ->sample66623D.BAM 

我已经试过：

for ((a=21;a<=23;a++)) 
    echo "zcat ~/tools/sample666$aD.fastq | bowtie2 -a - | samtools ->sample666$aD.BAM" 
done 

却原来是三个相同的线。

zcat ~/tools/sample666.fastq | bowtie2 -a - | samtools ->sample666.BAM 
zcat ~/tools/sample666.fastq | bowtie2 -a - | samtools ->sample666.BAM 
zcat ~/tools/sample666.fastq | bowtie2 -a - | samtools ->sample666.BAM 

感谢

Answer 1

$aD是一个有效的变量名。您必须用括号将变量名称分隔，即${a}。