Error dirname in shell script: Invalid option -- B

Error dirname in shell script: Invalid option -- B

When writing a Shell script today, an error is reported during debugging.

[Oracle @ smidb11 autoawrrpt] $. a. sh dirname: Invalid option -- B please try to execute "dirname -- help" for more information. Basename: Invalid option -- B. Please execute "basename -- help" to obtain more information.

The script content is as follows:

[Oracle @ smidb11 autoawrrpt] $ cat a. sh #! /Bin/bash #################################### ######################################## ##### automatically generate the latest AWR Report # version: v1.0 # variable Description: # LOGFILE: save the log file name ################################## modify history ####################################### ######################################## ###################################### WORKDIR = $ (dirname $0) # obtain the script directory cd $ {WORKDIR} # change the current directory to the script directory WORKDIR = 'pwd' # obtain the specific path of the current directory SCRIPTNAME =$ (basename $0) # obtain the Script Name FPATH = "$ {WORKDIR }\$ {SCRIPTNAME}" # full script path LOGFILE = "$ {WORKDIR}/$ {SCRIPTNAME }. log "# Set the log file name AWR_TYPE =" html "# Set the AWR type, the value should be html or txtAWR_HOME = "$ {WORKDIR}/awr_report" # Set the directory where AWR reports are stored AWR_DAYS = 1 # set the number of days for AWR Snap retrieval HOSTNAME = 'hostname' # host name mkdir -p $ {AWR_HOME} # If this directory does not exist, the "Create-p" option indicates that if no option is created, the system returns the result directly.

The error is reported in WORKDIR = $ (dirname $0), which makes me very strange. First, I didn't add the-B option after this command, why is the error option-B Reported?

Then add the echo $0 output under this line to see what the content of $0 is.

[Oracle @ smidb11 autoawrrpt] $. a. shdirname: Invalid option -- B please try to execute "dirname -- help" for more information. -Bashbasename: Invalid option -- B. Please execute "basename -- help" to obtain more information.

This is strange. Shouldn't $0 return the current path of the script? How can it be changed to-base?

We will try again:

[oracle@smidb11 autoawrrpt]$ ./a.sh ./a.sh

Run the command directly and the output result is correct. $0 indicates the relative path of the script to be executed.

Why is this problem? To prove this problem, we run echo $0 directly in the shell.

[mysql@test ~]$ echo $0-bash

Next, let's review the following commands in Linux:

Execute the script directly in the current shell when you execute the script using the dot command, instead of opening a new Shell to execute the script

It's hard to understand this. Because. the command does not open a new Shell to execute the script, so when echo $0, the value of $0 is still the original shell $0, that is,-bash, the basename command regards-bash as a parameter for execution, so an error is reported. The error option is-B.

Once we know the cause, our problem will be well solved. Run it directly. Do not run the script by clicking the command or source command.

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