Score:0

Server

how to extract a certain field from standard output with cut?

vrms

9/17/23, 2:10 PM

I have this output and want to extract the IMAGE ID from it

$ podman image ls | grep youtube-dl
localhost/youtube-dl          latest           2d4e37c4d609  3 hours ago    205 MB

All I know piping this to cut -f3 should to this but doesn't. The output is actually identical. All examples for cut I've found tell me that a tab (which applies here I believe) is assumed as delimiter.

Can anybody kindly point me to the right direction in this? Maybe I am falsely assuming the output uses tabs. I couldn't say what else however

0 + 0

linux

bash

pipe

Score:2

Server

Phill W.

9/17/23, 2:17 PM

Are you sure this out is tab delimited?
That would be quite unusual in a linux environment - whitespace delimiting is far more common.

Use one of the "awk" family of tools instead:

$ podman image ls | gawk '/youtube-dl/{print $3;}'
2d4e37c4d609

0 + 0

vrms

9/17/23, 2:24 PM

tx, that works. Never heard of those till today. Seems another field I have to explore.

Score:0

Server

Brahim Gaabab

9/17/23, 3:06 PM

There are many ways to do this. For instance, you can pipe your command output through cut while modifying the fiealds delimiter:

$ podman image ls | grep grep youtube-dl | tr -s ' ' | cut -d\ -f3

It is also possible to reveal the delimiter being used (e.g. TAB or space) by piping the output through od as in:

$ podman image ls | grep grep youtube-dl | od -An -c

0 + 0

glenn jackman

9/17/23, 3:32 PM

`cut -d" " -f3` doesn't work unless you squeeze the whitespace first: cut does not consider _sequences_ of the delimiter. `... | tr -s '[:blank:]' | cut -d" " -f3`

Brahim Gaabab

9/17/23, 7:20 PM

You are right about having delimiter sequences; they must be removed if any. I'll update, but target the space character only, i.e., not using the entire class.

vrms

9/18/23, 1:32 PM

this `$ podman image ls | grep grep youtube-dl | tr -s ' ' | cut -d\ -f3` does exactly what I was looking for, thx @BrahimGaabab @glenn_jackman (just as the `gawk` solution further up north).

Elon Musk

I sit in a Tesla and translated this thread with Ai:

EN: how to extract a certain field from standard output with cut?

TH: จะแยกฟิลด์ออกจากเอาต์พุตมาตรฐานด้วยการตัดได้อย่างไร

RO: cum se extrage un anumit câmp din ieșirea standard cu tăiere?

RU: как извлечь определенное поле из стандартного вывода с вырезом?

VI: làm cách nào để trích xuất một trường nhất định từ đầu ra tiêu chuẩn bằng cách cắt?

Post an answer

Most people don’t grasp that asking a lot of questions unlocks learning and improves interpersonal bonding. In Alison’s studies, for example, though people could accurately recall how many questions had been asked in their conversations, they didn’t intuit the link between questions and liking. Across four studies, in which participants were engaged in conversations themselves or read transcripts of others’ conversations, people tended not to realize that question asking would influence—or had influenced—the level of amity between the conversationalists.