Note that depending on what version of unix you're using, certain programs may behave a little differently (for example, ps might output the PID in column $3). If something seems wrong or different, read your vendor's documentation (or better, the man pages). Also be careful as long pipes can be dangerous.

I was wondering about differences and relation between redirection and pipeline. Is pipeline only used to connect stdout output of a command to stdin input of another command? Is redirection only used to connect a stdout output of a command to a file, and to connect a file to a stdin input of a command? But there seems to be command >& 2.

2017年1月17日 · @G-ManSays'ReinstateMonica' Good point. What the author wants - to be able to set environment variables in multiple segments of a pipeline, in bash, is impossible. Yet a selected answer exists - setting shopt -s lastpipe in bash, or using ksh.

2017年2月25日 · Pipeline use a pipe to link two file descriptors, typically standard output file descriptor of a command, and standard input file descriptor of the next command, thus the output of a command can be accessed by the command next to it. You can sequence infinite commands in this way to gradually process the data.

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I've a command that outputs data to stdout (command1 -p=aaa -v=bbb -i=4). The output line can have the following value: rate (10%) - name: value - 10Kbps I want to grep that output in order to store

2019年12月19日 · In a subsequent command in the same pipeline I might want to rename %28 as (. And I don't want to use a single rename command because of the regex complexity (if that's even possible). And I don't want to use a single rename command because of the regex complexity (if that's even possible).

But, back when Unix was created and children rode dinosaurs to school, disks were very small, and it was common for a rather benign command to consume all the free space in a file system. If B was something like grep some_very_obscure_string , the final output of the pipeline could be much smaller than that intermediate file.

2015年6月12日 · Just in addition to fredtantini and as a general clarification (since the docs are a bit confusing): The xargs -I {} will take the '{}' characters from the standard input and replace them with whatever comes in from the pipe.

2019年1月30日 · This is defined in the shell grammar, although not terribly clearly: the and_or production (for &&/||) is defined to have a a pipeline in its body, while pipeline just contains command, which doesn't contain and_or - only the complete_command production can reach and_or, and it only exists at the top level and inside the bodies of structural constructs like functions and loops.