Database accidentally deleted with a bash script

Easy enough. The // sequence isn't a comment in bash (# is).

The statement OUT_DIR=x // text had no effect* except a cryptic error message.

Thus, with the OUT_DIR being an empty string, one of the commands eventually executed was rm -rf /*. Some directories placed directly underneath / weren't removed due to user not having permissions, but it appears that some vital directories were removed. You need to restore from backup.

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* The peculiar form of bash statement A=b c d e f is roughly similar to:

export A=b
c d e f
unset A

A common example:

export VISUAL=vi                       # A standard visual editor to use is `vi`
visudo -f dummy_sudoers1               # Starts vi to edit a fake sudo config. Type :q! to exit
VISUAL=nano visudo -f dummy_sudoers2   # Starts nano to edit a fake sudo config
visudo -f dummy_sudoers3               # Starts vi again (!)

And the problematic line of script amounted to this:

export OUT_DIR=/data/backup/mongod/tmp
// 备份文件临时目录   # shell error as `//` isn't an executable file!
unset OUT_DIR

1) He erroneously assumed that // was a bash comment. It is not, only # is.

The shell interpreted // text as a normal command, and did not find a binary called //, and did nothing.

In bash, when you have a variable assignment (OUT_DIR=/data/backup/mongod/tmp) directly preceding a command (// text), it only sets the variable while running the command. Therefore, it unsets OUT_DIR immediately, and when the rm line is reached, OUT_DIR is now unset, and rm -rf / is now called, deleting everything you have permission to delete.

2) The solution is the same as all rm -rf / cases: restore from backup. There is no other solution because you do not have physical access to the hard drive.

1) Bash comments start with #. Sorry for your loss. 2) Restore from backup is the only way to proceed here, unfortunately.