Questions tagged [command-substitution]
Command substitution is the replacement of a command with the result returned after it is evaluated.
command-substitution
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Bash command substitution issues
I'm writing a Python script to parse various logs across different hosts.
I can successfully run bash scripts via Python's subprocess module, however, I want to minimize the number of ssh calls, so I'...
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Bash dialog: chained command substitution if problem
I want to write a script based on dialog programbox (or others) and capture a command's stderr and the stdout passed to dialog into an array (if any), as well as the command's exit status (as last ...
- 117
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Sed's append command (a) is for some reason deleting all file's text and then appending the provided text
I'm trying with GNU sed command to append a line into a file inside a block/section, specifically just a line under the start of the block/section. As a result it empties the file (maybe leaves a ...
- 21
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I am having trouble using the date function along with the vim command in bash
I have recently started journaling and I wanted to create a program to make the process a little easier. The program uses bash to mount an external hard drive (with a known name) and open the journal ...
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A crontab fails to run a task with a date command
In a project, I am trying to run a command that processes data from the day before (a rather common use case).
I am running it from a Docker container (python:3.11 derived) and therefore a Linux ...
- 689
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Fail bash script when command expansion fails
I'd like to be able to warn and fail if the following command expansion fails:
#!/usr/bin/env bash
set -Eeuo pipefail
echo "$(invalid_cmd)"
echo "$?"
Instead of failing, I get ...
- 2,748
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Expansion in an eval variable
Is it possible to do expansion inside an eval variable?
Example:
$ eval VAR=`echo some/path/{file1,file2}`
bash: some/path/file2: No such file or directory
I expected the same result as without using ...
- 11
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Openssl return values in bash scripts
Openssl 3.0.2.15 on Ubuntu Server (current)
So, my forensics class was working on a problems I used for bash and we found a kind of strange thing. If you are trying to detect a valid password using a ...
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Order of Command substitution and Arithmetic expansion in bash
The book “Learning the bash Shell” 3rd ed. by Cameron Newham and Bill Rosenblatt has at page 181 a picture describing the command-line processing of bash shell. That picture shows that Command ...
- 67
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assign output of a cat | sed | awk to an array
Updated Question with code.
I have written a script that retrieves files from a remote server via scp. Then I want the script to delete the success file that has been retrieved.
But instead of ...
- 61
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How can I nest $(var) variable command substitutions?
I have a need to update a bash/perl script to create a file with a system process (mktemp), I need to set the filename for creation, and for this I want to use the current system date:
LOGFILE=$(/bin/...
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Kubernetes CronJob - Escaping a cURL command with nested JSON and command substitution
I have the following Kubernets CronJob definition:
apiVersion: batch/v1
kind: CronJob
metadata:
name: myCronJob
spec:
schedule: "*/1 * * * *"
failedJobsHistoryLimit: 1
...
- 2,362
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BASH: Variables in a function piped to dialog are lost
I have a script with a function which does some stuff and sets some variables to be used later in the script. This function is also echoing progress (echo 10, echo 20 etc.) and is piped to a "...
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how do I get rid of the single quotes around my string
I have a zsh script. There is a function ...
imgPrep()
{
local inFilePath=$1
local outFilePath=$2
local cropHeight=$3
local resize=$4
shift; shift; shift; shift
local options=$@
convert ${inFilePath} ...
