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Yes. Thanks, most of the last two years of using CLI have all been using "single specific scripts", so I'm getting sick of not actually knowing how CLI works a

Yes. Thanks, most of the last two years of using CLI have all been using "single specific scripts", so I'm getting sick of not actually knowing how CLI works and being a confused, brainless C&P robot. Everybody who writes the tutorials and provides me with the scripts seem to know what they are doing, but it is hard to figure it out. Thanks for the link. In terms of specifics, it is the ones I mention at the bottom of the post, regarding finding EBS blocks with lsblk, passing the names into an MDADM command, and then the rest of the script doesn't need anything more dynamic. I will look up grep/sed/awk (I'm writing a bash script). From what I know of them so far, they are just regexp, which concerns me, because that feels like a very dangerous "hacky" way of performing very delicate and important tasks. But it seems that everybody is saying that is the only way to handle outputs. Anything else? Thanks for your help.

ColinWright 14y ago
This is going to look like a rant. In a way it is, but I am honestly trying to help you, not just in this issue, but also in getting help in general. Bear with me. OK, so it looks to me like you didn't actually answer the questions I asked. In particular, I asked: > * What is the first command you're running? > * What output do you get? > * From that, what command do you want to construct? I also said: > Be clear, precise, specific, ... You are asking me for help, I have indicated that I'm willing to help you, but you aren't actually answering the questions I ask, and it appears that you're not actually paying attention to what I write. If I'm going to give up some of my time to help you, someone I've never met, then you really, really should make it easy for me. Instead you've made me go back to the original posting on StackOverflow and try again to understand the exact question, even though I've clearly asked for some clarification. For example: > lsblk -l -list_the_names_of_blocks_not_mounted I know nothing about the lsblk command, I don't know if these are real parameters or part of the "pseudo code" you've invented to explain your problem, and I certainly don't know what you're expecting it to output. So let me repeat: > * What is the first command you're running? > * What output do you get? I assume (and it appears that you've confirmed) that you need to extract some information from the output and use it to construct a new command. That's pretty easy to do and I'll happily talk you through the process. Mostly these processes use standard tools like grep, sed, and awk, but it would appear at the time of writing that all you have of them is a negative impression that "they are just regexp" and as such that "feels like a very dangerous 'hacky' way of performing very delicate and important tasks." Perhaps you should judge that after you've actually seen them in operation for real. If you still consider them "hacky" then you will have acquired enough information to do it all in Python (or other languages) if you choose. So, if you'd still like me to help, please re-read this reply carefully, in full, and you'll know how to proceed. Added in edit: I've just read your comment on the one reply you've had over there, and now I really don't know what you're expecting. In the CLI you can take the output of one command and feed it into a pipeline that does stuff to it. What more are you expecting than tools designed to work with a pipeline of text?
- marknadal 14y ago
  Thanks, Colin. 1) MDADM requires specific parameters in order to mount physical drives into a virtual RAID drive. 2) Meaning, piping outputs doesn't work, since the text that is output does not equal the parameters needed. 3) First, the script has to automatically determine which drives should be used. This is done by calling lsblk -l (easier to parse than fdisk) and looking for non-mounted partitions. It outputs: NAME MAJ:MIN RM SIZE RO MOUNTPOINT sr0 11:0 1 49.8M 0 /media/VBOXADDITIONS_4.1.18_78361 sda 8:0 0 8G 0 sda1 8:1 0 7.5G 0 / sda2 8:2 0 1K 0 sda5 8:5 0 510M 0 [SWAP] 4) MDADM's command parameter is the following: sudo mdadm --create --verbose /dev/md0 --level=10 --chunk=256 --raid-devices=$RNUM $DRIVES Where $RNUM is an integer corresponding to the number of drives, and $DRIVES is a space-separated list of the paths to the unmounted drives (which should probably further be filtered on size, since one of them is only 1K but let's ignore its size for now). We also have to remember to prefix '/dev/' since that is where the drives are mounted onto. So explicitly: DRIVES=/dev/sda /dev/sda2 RNUM=2 Which then makes: 5) sudo mdadm --create --verbose /dev/md0 --level=10 --chunk=256 --raid-devices=2 /dev/sda /dev/sda2 Notes: a) I've been able to accomplish this using node, since in JS I can just do things like string.split(" ") and get an array which I can loop through, or split on newlines, or whatever. But I don't know how this is accomplished in bash scripting. Thanks for helping out somebody very unintelligent with respect to CLI, despite the last year and a half being fully involved, and trying to google the help out of every issue and tutorials. I hope some day I'll be good enough to help teach people as well.

ColinWright 14y ago

This is going to look like a rant. In a way it is, but I am honestly trying to help you, not just in this issue, but also in getting help in general. Bear with me. OK, so it looks to me like you didn't actually answer the questions I asked. In particular, I asked: > * What is the first command you're running? > * What output do you get? > * From that, what command do you want to construct? I also said: > Be clear, precise, specific, ... You are asking me for help, I have indicated that I'm willing to help you, but you aren't actually answering the questions I ask, and it appears that you're not actually paying attention to what I write. If I'm going to give up some of my time to help you, someone I've never met, then you really, really should make it easy for me. Instead you've made me go back to the original posting on StackOverflow and try again to understand the exact question, even though I've clearly asked for some clarification. For example: > lsblk -l -list_the_names_of_blocks_not_mounted I know nothing about the lsblk command, I don't know if these are real parameters or part of the "pseudo code" you've invented to explain your problem, and I certainly don't know what you're expecting it to output. So let me repeat: > * What is the first command you're running? > * What output do you get? I assume (and it appears that you've confirmed) that you need to extract some information from the output and use it to construct a new command. That's pretty easy to do and I'll happily talk you through the process. Mostly these processes use standard tools like grep, sed, and awk, but it would appear at the time of writing that all you have of them is a negative impression that "they are just regexp" and as such that "feels like a very dangerous 'hacky' way of performing very delicate and important tasks." Perhaps you should judge that after you've actually seen them in operation for real. If you still consider them "hacky" then you will have acquired enough information to do it all in Python (or other languages) if you choose. So, if you'd still like me to help, please re-read this reply carefully, in full, and you'll know how to proceed. Added in edit: I've just read your comment on the one reply you've had over there, and now I really don't know what you're expecting. In the CLI you can take the output of one command and feed it into a pipeline that does stuff to it. What more are you expecting than tools designed to work with a pipeline of text?

marknadal 14y ago
Thanks, Colin. 1) MDADM requires specific parameters in order to mount physical drives into a virtual RAID drive. 2) Meaning, piping outputs doesn't work, since the text that is output does not equal the parameters needed. 3) First, the script has to automatically determine which drives should be used. This is done by calling lsblk -l (easier to parse than fdisk) and looking for non-mounted partitions. It outputs: NAME MAJ:MIN RM SIZE RO MOUNTPOINT sr0 11:0 1 49.8M 0 /media/VBOXADDITIONS_4.1.18_78361 sda 8:0 0 8G 0 sda1 8:1 0 7.5G 0 / sda2 8:2 0 1K 0 sda5 8:5 0 510M 0 [SWAP] 4) MDADM's command parameter is the following: sudo mdadm --create --verbose /dev/md0 --level=10 --chunk=256 --raid-devices=$RNUM $DRIVES Where $RNUM is an integer corresponding to the number of drives, and $DRIVES is a space-separated list of the paths to the unmounted drives (which should probably further be filtered on size, since one of them is only 1K but let's ignore its size for now). We also have to remember to prefix '/dev/' since that is where the drives are mounted onto. So explicitly: DRIVES=/dev/sda /dev/sda2 RNUM=2 Which then makes: 5) sudo mdadm --create --verbose /dev/md0 --level=10 --chunk=256 --raid-devices=2 /dev/sda /dev/sda2 Notes: a) I've been able to accomplish this using node, since in JS I can just do things like string.split(" ") and get an array which I can loop through, or split on newlines, or whatever. But I don't know how this is accomplished in bash scripting. Thanks for helping out somebody very unintelligent with respect to CLI, despite the last year and a half being fully involved, and trying to google the help out of every issue and tutorials. I hope some day I'll be good enough to help teach people as well.