Questions tagged [variable-substitution]
The variable-substitution tag has no usage guidance.
222
questions
1
vote
1answer
31 views
Providing Bash substitution as a function argument
I have a following loop that works well:
function uppercase_all_letters() {
for filename in *;
do echo "${filename^^}";
done;
}
How do I provide "${filename^^}" as a parameter to the ...
1
vote
1answer
32 views
Makefile commands with external args and internal variables
In a Makefile target I have a list of files that I want to split into x parts and work only with one part y, then pass those file names as argument to a test runner. I have no control over the ...
0
votes
0answers
37 views
Why can't execute ls or cp commands with a variable as an argument [duplicate]
I am debugging a bash script. It executes cp and mv commands in the script when a variable containing a path is used as the argument to the command. I have duplicated it in the terminal as follows:
...
-2
votes
2answers
74 views
How to execute a command that has many nested single and double quotes with a quoted variable in bash
Here is my simple script
#!/bin/sh
thefile=/home/ark/arkserver/ShooterGame/Saved/SaveIsland/1288804998.arktribe
while inotifywait "${thefile}" ; do
a=\"`strings ${thefile} | tail -n 5 | head -n ...
5
votes
1answer
936 views
Bash echo $-1 prints hb1. Why?
If I ask bash to echo the -1th argument it prints hb1:
echo $-1
hb1
Why? What is it accessing?
3
votes
1answer
2k views
Is `echo $TEST` expanding an asterisk in the variable a bug? [duplicate]
Is this a Bash bug?
$ mkdir test && cd test && echo "a" > "some.file"
test$ echo '*'
*
test$ TEST=$(echo '*')
test$ echo $TEST
some.file
Why is the second output the resolution of ...
1
vote
1answer
76 views
cp runs from command line but file not found from script [duplicate]
I have a script to reorganize my directory structure that contains:
files=./*"$pattern"I{"$ifirst".."$ilast"}.ext
cp ${files} ../"$pattern"/"$i"/
When I run the script, I get an error:
./*S6I{001.....
1
vote
0answers
31 views
!$ vs $_ difference? [duplicate]
In GNU Bash, both !$ and $_ expands to the last argument of the last command.
I think they're identical and I need someone to tell me if there is any difference.
7
votes
5answers
939 views
Using parameter substitution on a Bash array
I have file.txt that I need to read into a Bash array. Then I need to remove spaces, double quotes and all but the first comma in every entry. Here's how far I've gotten:
$ cat file.txt
10,this
2 0 ...
2
votes
1answer
59 views
Combine brace and variable expansion in one line
I would like to have a logging function that takes filenames as arguments and replicate the stdout to all of these files. This is what I have come up so far:
function logger() {
exec > >(...
0
votes
0answers
144 views
Use variable inside sed command [duplicate]
how can i use variables inside this sed command?
sed -i.bak -e '/triggerword/,${w $DIR/tempfile' -e 'd;}' $DIR/targetfile
inside -e '{w $DIR/tempfile' -e 'd;}' the $DIR/tempfile isn't recognized
0
votes
1answer
81 views
why curl can't expand variable inside the loop, but echo can?
I need to include variable inside curl
for fname in "assets/*.drx"; do
echo $fname
curl -F file=@"$fname" "http://someurl.com/"
echo $fnamename
done
Result:
assets/...
10
votes
1answer
471 views
What does the substitution ${!var_name+x} mean?
I found a script that has a function that checks if a variable is set but i don't understand it very well.
check_if_variable_is_set() {
var_name=$1
if [ -z "${!var_name+x}" ]; then
...
0
votes
3answers
569 views
Modifying a shell variable with regex (bash)
I have a shell variable for example. a="big little man". How do I use regex in bash print out the variable with only the middle word capitalized? (big LITTLE man)
I can do it by separating the ...
0
votes
2answers
62 views
How can I export a variable in bash where the variable name is comprised of two variables?
I'm trying to export variables inside of a for loop where I wanted each iteration of the loop to change what variable was being written to. I've been looking for the right syntax to satisfy exporting ...
0
votes
1answer
233 views
Bad substitution when running from cron
I have a function (notify_dba) that with two string args, a header and a body. (correction) Works well from shell prompt, but not in cron Err, doesn't work in either shell or cron (but should...?):
...
2
votes
1answer
26 views
How can I build an env file (with $ characters) listing as-is from echo command?
I am trying to build a file invoked from a script that echoes what is in quotes to a file - only, the $ gets omitted.
This is what I was trying to do:
echo -e "export ORACLE_BASE=/oracle/APP/grid \n ...
0
votes
0answers
13 views
Interaction of sed and for loop [duplicate]
for i in {1..25}; do cat file$((i)) | sed 's/.*/$((i))/'; done
doesn't print the current value of i but just $((i)). How can I make it print the value of i instead?
0
votes
2answers
76 views
Running multiple command against files matching a brace+glob pattern without repeating it
I would like to run a series of commands against a set of files matched by a braces-and-globs pattern, without copy-pasting the pattern all over the place. I've been trying to do this by putting the ...
1
vote
1answer
33 views
Zsh: check existing of file before expanding
In Zsh parameter expansion, I have:
"${test_var:-"${HOME}/test"}"
but here I want to check if ${HOME}/test is exist or not, if not exist then test_var expand to " " (one space string).
Is there an ...
5
votes
0answers
85 views
Correct treatment of quotes in parameter expansions
Using the default value of IFS, consider
unset var
set -- ${var:-"hello"}
echo "$#"
This prints 1 as the parameter expansion expands to the single string hello.
unset var
set -- "${var:-"hello"}"
...
0
votes
1answer
29 views
Can variable-substitution-syntaxes be unified?
Can these two variable-substitution-syntaxes combined into one?
rm "$s_a/$domain.conf" 2>/dev/null
rm "$s_e/$domain.conf" 2>/dev/null
like:
rm "$s_{a,e}/$domain.conf" 2>/dev/null
1
vote
1answer
1k views
using variables inside the curl command not working in bash script
I am trying to write a bash script to update certain nodes in my repository. I wrote below script, but it does not seem to be working when I use variables inside curl. Below is the code. I tried all ...
3
votes
2answers
294 views
Bash parameter substituiton within commands
I have a passing understanding of Parameter Substitution, including substrings like so
foo="Hello World";
greeting=${foo:0:6}
But do I do this with commands?
greeting="Hello"
md5greeting=$(echo $...
3
votes
4answers
778 views
awk - replace number greater than 17 digits in a column with -
I have a CSV file containing timestamp values in UTC which I need to replace with -. There may be more than one timestamp in the same column, can you please let me know how do I do that?
For example, ...
0
votes
4answers
42 views
substitutions in vi editor
I have file called foo.txt. This file contains values:
abc.tar.gz
abc.1.1.tar.gz
bca-1.2.tar.gz
I would like to get an output like this
abc abc.tar.gz
abc.1.1 abc.1.1.tar.gz
bca-1.2 bca-1.2.tar.gz
...
1
vote
1answer
536 views
Makefile: Copy using make variables --> error; Not so without variables!
In the following makefile
InputLocation:=./Test
OutputLocation:=$(InputLocation)/Output
Input:=$(wildcard $(InputLocation)/*.md)
Output:=$(patsubst $(InputLocation)/%, $(OutputLocation)/%, $(Input:...
0
votes
2answers
35 views
How do I append a date to a file using Bash script with multiple variables?
My script is below, I can't remember how to make this make sense.
#!/bin/bash
input=$1
output=$2
cp $input $output_$(date +%m%d%y)
The goal is to run the script as follows
/path/script.sh /path/...
1
vote
3answers
212 views
Dynamic variables in shell
I have a following script that will take input (source path) from user and it will attach the volume inside docker container
echo -n "Enter the source path: "
read path
docker run -v $path:/opt/$...
1
vote
1answer
661 views
Glob character within variable expands in bash but not zsh
I'm seeing an issue with zsh where a glob character within a variable is not expanding as I would expect. The following example does a better job of explaining it.
$ echo $0
-bash
$ echo $HOME/...
0
votes
2answers
160 views
Using shell 'printf' where the format string is in a variable and doesn't have a fixed number of field placeholders?
I am writing a shell function which makes an external API call via cURL (the external API syntax isn't under my control). I've approached it like this (simplified):
#!/bin/sh
template_get_entry='...
0
votes
2answers
864 views
Passing an argument with double and single quotes to another call in bash [closed]
I have a call
./run.sh name --vars="service_name='someothername'"
and I'm trying to call another program with exactly same --vars="service_name='someothername'" argument from run.sh, however when ...
13
votes
4answers
3k views
Is it possible to print the content of the content of a variable with shell script? (indirect referencing)
Let's suppose I've declared the following variables:
$ var='$test'
$ test="my string"
If I print their contents I see the following:
$ echo $var
$test
$ echo $test
my string
I'd like to find a ...
1
vote
0answers
140 views
Bash variable value partially substituted in Curl input
Below is my shell script in which I'm trying to use the value of a variable as input to curl. However, the script is giving an error and when trying to debug the script, I can see that the value of ...
5
votes
3answers
236 views
How to create a loop with five (5) input variables?
I have a proprietary command that requires five (5) inputs to properly execute the command.
command -cval <value> -tval <value> -dval <value> -kval <value>
I need to be able ...
0
votes
2answers
484 views
${p:2:1} Meaning in the shell script
Can anyone tell me the meaning of ${p:2:1} in shell scripting as in:
var1=""
for p in [1,2,3,4]
do
var1="${var1} ${p:2:1}"
done
2
votes
0answers
76 views
What are the contexts where Bash doesn't perform word splitting and globbing?
Bash doesn't perform word splitting in globbing in these cases:
LHS or RHS of an assignment, except for indexed arrays
var=$value # simple variable
declare -A hash
key=...
0
votes
2answers
89 views
for loop variable assignment with whitespaces
Im collecting the LPAR names and assigning to a variable on AIX , Then using multiple commands for processing.
LPAR Names on the system are : ABCD56777 TSM Mobile CD CPT 2
for lparname in `...
7
votes
2answers
1k views
calling other variables in a variable name (Bash)
At the moment I have the next paths
langs="EN GE"
dir_EN=/xx
dir_GE=/zz
As you can see the variable $langs has all possible languages in a single array. I would like to save all those paths in a ...
0
votes
2answers
75 views
Automating wp-config.php creation
I use Ubuntu 16.04 with Bash and I tried to run the following command set to automatically create a WordPress wp-config.php file with the WordPress Bash extension WP-CLI. Yet I'm having some problem I ...
0
votes
3answers
37 views
Variable in variable expansion
I want to evaluate a variable, whose name will need to dynamically evaluate another varuiable, i.e. the var ENVIRONMENT can be either prod, stg, or test, so I have 3 urls:
URL_PROD=https://...
0
votes
1answer
213 views
Variable Expansion Adding Braces to Original String Value [closed]
NOTE: I missed a syntax issue in my script that was causing this. I was passing ${bar} as {$bar}. This can be removed or locked or whatever is done with these types of questions.
I'm trying to test ...
2
votes
2answers
75 views
Using variable values defined in one file, in files in the same directory
In this GitHub repository I have a directory named nwsm. This directory contains the file nwsm.sh that contains a master script (a script that runs other scripts).
The directory also contains a few ...
1
vote
1answer
200 views
Basic usage of /etc/cron/ (d): correct pattern for /etc/cron (daily/weekly/monthly)
I use Ubuntu 16.04 with Bash and I've created this extensionless, shebangless file /etc/cron.daily/cron_daily:
for dir in "$drt"/*/; do
if pushd "$dir"; then
wp plugin update --all --allow-root
wp ...
0
votes
0answers
41 views
Variable expansion succeeds with echo but fails without a command (execution by expansion) [duplicate]
I created a file nano ~/uncwe/configurations/variables.sh. This file contains:
set -a
rse="~/${repo}/internal_software/rse.sh"
set +a
I sourced the file, then tried to execute:
${rse}
bash ${rse}
...
1
vote
3answers
345 views
Trivial rm -rf command destroys my operating system in a testing machine
I use Bash 4.3.48(1) and I ran the following command pattern on a testing VPS machine:
rm -rf ${drt}/${pma}*
This command deleted the entire operating system (Ubuntu). That was evident by executing ...
3
votes
2answers
314 views
cat-redirect a file, but with variable expansions
I have the file ~/nginx_app containing this conf template:
server {
root /var/www/html/${domain}/;
server_name ${domain} www.${domain};
}
I also have this script:
#!/bin/bash
domain="$1" &...
0
votes
3answers
3k views
Reference bash variable from a variable [duplicate]
How can I reference a variable in bash based on another variable? Let me setup the example:
package="foobar"
# the variable I wish to reference is $foobar_darwin_amd64
# thus trying:
echo "$...
9
votes
9answers
4k views
Bash: Extract one of the four sections of an IPv4 address
We can use the syntax ${var##pattern} and ${var%%pattern} to extract the last and first section of an IPv4 address:
IP=109.96.77.15
echo IP: $IP
echo 'Extract the first section using ${var%%pattern}: ...
4
votes
4answers
4k views
Backslash in variable substitution in Bash
I was working on a Bash script to help partition a hard drive correctly, and I came across a strange problem where I had to append a number to a variable. It took me a while to get the outcome right ...
