bash：替换错误

Question

#!/bin/bash

jobname="job_201312161447_0003"
jobname_pre=${jobname:0:16}
jobname_post=${jobname:17}

This bash script gives me Bad substitution error on ubuntu. Any help will be highly appreciated.

Answer 1

The default shell ( /bin/sh ) under Ubuntu points to dash , not bash .

me@pc:~$ readlink -f $(which sh)
/bin/dash

So if you chmod +x your_script_file.sh and then run it with ./your_script_file.sh , or if you run it with bash your_script_file.sh , it should work fine.

Running it with sh your_script_file.sh will not work because the hashbang line will be ignored and the script will be interpreted by dash , which does not support that string substitution syntax.

Answer 2

I had the same problem. Make sure your script didnt have

#!/bin/sh 

at the top of your script. Instead, you should add

#!/bin/bash

Answer 3

对于到达这里的其他人，使用 env 变量语法进行命令时也会出现此确切消息，例如${which sh}而不是正确的$(which sh)

Answer 4

Your script syntax is valid bash and good.

Possible causes for the failure:

1. Your bash is not really bash but ksh or some other shell which doesn't understand bash's parameter substitution. Because your script looks fine and works with bash. Do ls -l /bin/bash and check it's really bash and not sym-linked to some other shell.

2. If you do have bash on your system, then you may be executing your script the wrong way like: ksh script.sh or sh script.sh (and your default shell is not bash). Since you have proper shebang, if you have bash ./script.sh or bash ./script.sh should be fine.

Answer 5

尝试使用 bash 命令显式运行脚本，而不仅仅是将其作为可执行文件执行。

Answer 6

Also, make sure you don't have an empty string for the first line of your script.

ie make sure #!/bin/bash is the very first line of your script.

Answer 7

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. Eg bash -c '${x }'
• A typo. Eg bash -c '${x;-}'
• A feature that was added in a later Bash version. Eg 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. Eg:

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

Answer 8

Both - bash or dash - work, but the syntax needs to be:

FILENAME=/my/complex/path/name.ext
NEWNAME=${FILENAME%ext}new

Answer 9

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

Answer 10

我发现这个问题要么是由标记的答案引起的，要么是在 bash 声明之前有一行或一个空格

Answer 11

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

Answer 12

#!/bin/bash

jobname="job_201312161447_0003"
jobname_pre=${jobname:0:16}
jobname_post=${jobname:17}

This bash script gives me Bad substitution error on ubuntu. Any help will be highly appreciated.

Answer 13

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 .

Answer 14

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#