bash : Bad Substitution

Not relevant to your example, but you can also get the Bad substitution error in Bash for any substitution syntax that Bash does not recognize. This could be:

• Stray whitespace. E.g. bash -c '${x }'
• A typo. E.g. bash -c '${x;-}'
• A feature that was added in a later Bash version. E.g. bash -c '${x@Q}' before Bash 4.4.

If you have multiple substitutions in the same expression, Bash may not be very helpful in pinpointing the problematic expression. E.g.:

$ bash -c '"${x } multiline string
$y"'
bash: line 1: ${x } multiline string
$y: bad substitution

I was adding a dollar sign twice in an expression with curly braces in bash:

cp -r $PROJECT_NAME ${$PROJECT_NAME}2

instead of

cp -r $PROJECT_NAME ${PROJECT_NAME}2

I have found that this issue is either caused by the marked answer or you have a line or space before the bash declaration

Looks like "+x" causes problems:

root@raspi1:~# cat > /tmp/btest
#!/bin/bash

jobname="job_201312161447_0003"
jobname_pre=${jobname:0:16}
jobname_post=${jobname:17}
root@raspi1:~# chmod +x /tmp/btest
root@raspi1:~# /tmp/btest
root@raspi1:~# sh -x /tmp/btest
+ jobname=job_201312161447_0003
/tmp/btest: 4: /tmp/btest: Bad substitution

in my case (under ubuntu 18.04), I have mixed $( ${} ) that works fine:

BACKUPED_NB=$(ls ${HOST_BACKUP_DIR}*${CONTAINER_NAME}.backup.sql.gz | wc --lines)

full example here.

I used #!bin/bash as well tried all approaches like no line before or after #!bin/bash.
Then also tried using +x but still didn't work. Finally i tried running the script ./script.sh it worked fine.

#!/bin/bash
jobname="job_201312161447_0003"
jobname_post=${jobname:17}

root@ip-10-2-250-36:/home/bitnami/python-module/workflow_scripts# sh jaru.sh
jaru.sh: 3: jaru.sh: Bad substitution

root@ip-10-2-250-36:/home/bitnami/python-module/workflow_scripts# ./jaru.sh
root@ip-10-2-250-36:/home/bitnami/python-module/workflow_scripts#