观看流程替换

Question

我经常运行命令

squeue -u $USER | tee >(wc -l)

其中 squeue 是 Slurm command 以查看您运行有多少工作。这给了我 squeue 的输出，并自动告诉我其中有多少行。

我如何watch这个命令？

watch -n.1 "squeue -u $USER | tee >(wc -l)" 结果

Every 0.1s: squeue -u randoms | tee >(wc -l)                                                                                                                                                                                                                                                                                                        Wed May  9 14:46:36 2018

sh: -c: line 0: syntax error near unexpected token `('
sh: -c: line 0: `squeue -u randoms | tee >(wc -l)'

Answer 1

来自 watch 手册页：

Note that command is given to "sh -c" which means that you may need to use extra quoting to get the desired effect.

sh -c 也不支持进程替换，您在此处使用的语法为 >().

幸运的是，您正在做的事情实际上并不需要该语法：

watch -n.1 'out=$(squeue -u "$USER"); echo "$out"; { echo "$out" | wc -l; }'

...或者，如果您真的想要使用您的原始代码，即使性能损失很大（开始时不只是一个，而是两个每十分之一秒发射一次新炮弹——首先是 sh，然后是 bash):

bash_cmd() { squeue -u "$USER" | tee >(wc -l); } # create a function
export -f bash_cmd            # export function to the environment
watch -n.1 'bash -c bash_cmd' # call function from bash started from sh started by watch

观看流程替换

Watch with Process Substitution

bash

unix

watch

process-substitution