I want to run this script:
#!/bin/bash
echo <(true)
I run it as:
sh file.sh
And I get "Syntax error: "(" unexpected" . I found some similar situations but still can't solve this.
I'm a beginner at shell scripting , but as I understand:
the shebang I use is correct and chooses the bash shell , so the process substitution syntax should work
I try the same from the command line and it works. I checked with echo $0 and it gives me "bash" , so what's the difference from running the command in the command line and from a script that invokes the same shell?
Maybe it's something simple, but I couldn't find an explanation or solution.
You should run your script with bash, i.e. either bash ./script.sh or making use of the shebang by ./script.sh after setting it to executable. Only running it with sh ./script.sh do I get your error, as commented by Cyrus.
See also: role of shebang at unix.SE
Remove export POSIXLY_CORRECT=1 from your ~/.bashrc or ~/.profile (etc.) files.
The issue is that process substitution is an added bash feature that is not part of the posix standards.
sh file.sh
errorsh: 3: Syntax error: "(" unexpected
solution:
bash file.sh
Related
I want to run this script:
#!/bin/bash
echo <(true)
I run it as:
sh file.sh
And I get "Syntax error: "(" unexpected" . I found some similar situations but still can't solve this.
I'm a beginner at shell scripting , but as I understand:
the shebang I use is correct and chooses the bash shell , so the process substitution syntax should work
I try the same from the command line and it works. I checked with echo $0 and it gives me "bash" , so what's the difference from running the command in the command line and from a script that invokes the same shell?
Maybe it's something simple, but I couldn't find an explanation or solution.
You should run your script with bash, i.e. either bash ./script.sh or making use of the shebang by ./script.sh after setting it to executable. Only running it with sh ./script.sh do I get your error, as commented by Cyrus.
See also: role of shebang at unix.SE
Remove export POSIXLY_CORRECT=1 from your ~/.bashrc or ~/.profile (etc.) files.
The issue is that process substitution is an added bash feature that is not part of the posix standards.
sh file.sh
errorsh: 3: Syntax error: "(" unexpected
solution:
bash file.sh
I want to run this script:
#!/bin/bash
echo <(true)
I run it as:
sh file.sh
And I get "Syntax error: "(" unexpected" . I found some similar situations but still can't solve this.
I'm a beginner at shell scripting , but as I understand:
the shebang I use is correct and chooses the bash shell , so the process substitution syntax should work
I try the same from the command line and it works. I checked with echo $0 and it gives me "bash" , so what's the difference from running the command in the command line and from a script that invokes the same shell?
Maybe it's something simple, but I couldn't find an explanation or solution.
You should run your script with bash, i.e. either bash ./script.sh or making use of the shebang by ./script.sh after setting it to executable. Only running it with sh ./script.sh do I get your error, as commented by Cyrus.
See also: role of shebang at unix.SE
Remove export POSIXLY_CORRECT=1 from your ~/.bashrc or ~/.profile (etc.) files.
The issue is that process substitution is an added bash feature that is not part of the posix standards.
sh file.sh
errorsh: 3: Syntax error: "(" unexpected
solution:
bash file.sh
I am trying to play with bash and arrays. But executing a sample script, I got an unexpected syntax error message: example.sh: 3: example.sh: Syntax error: "(" unexpected. And this is the script
#!/bin/bash
array=( one two three )
If I run the script with ./example.sh it works and no errors are displayed. But if I run sh example.sh I get the error message.
I thought that these two commands are the same:
sh example.sh
./example.sh
so ... what is the difference between the two?
When you launch it via ./example.sh then the command specified in the first line of the script is used to interpret the content. So your script executes in a bash, where such syntax is allowed for arrays.
When you launch it via sh example.sh then sh is the command that is used to interpret the content of the file. sh is the original Unix shell (aka Bourne shell) and this shell is a little more rude than bash (Bourne again shell). You don't have such arrays. Note that in sh the first line of your script is just interpreted as a comment.
by using sh example.sh
- you are specifying what shell interpreter to use for that script. Example being "bash example.sh" instead of "sh example.sh" etc etc.
Running scripts this way disregards the "shebang (#!/bin/bash)" that you have specified inside of the script. Since you wrote a bash script but are trying to run it as just "sh", this is why it is failing
by using ./example.sh,
- You are specifying to run the script from your current directory. This will attempt to run the script in whatever shell you are currently in unless a shebang is specified. Since you have a "shebang" specified to run the script in bash... this is why it is working.
array_name=(value1 ... valuen)
This is how to initializes an array in bash only. When you execute ./example.sh, the shebang line #!/bin/bash tells the system to use bash to execute.
However, when you execute sh example.sh, sh is used to execute. In many Unix systems (like Linux), sh is equivalent to bash. It seems sh is a different shell on your system.
I'm writing a shell script called myShellScript.sh inside of which I have the following text:
echo *** Print out this line ****
diff <(./myProgram) <(./otherProgram)
However, when I run sh myShellScript.sh I get the following error:
-bash-4.2$ sh myShellScript.sh
myShellScript.sh **** Print out this line **** myShellScript.sh
myShellScript.sh: line 2: syntax error near unexpected token `('
myShellScript.sh: line 2: `diff <(./myProgram) <(./otherProgram)'
Process substitution with the <(...) operator is a bash feature. You're getting that error message because your script is getting executed as something else (for example dash), or an older version of bash, or bash running in POSIX-compatibility mode with non-POSIX features like process substitution disabled (thanks, #chepner!)
If you want to execute the script with a full-featured bash, you have two options:
Run the script with bash:
bash myShellScript.sh
Set the first line of the script to #!/bin/bash (or whatever is the path to bash in your system), and run the script like this:
./myShellScript.sh
You need to execute your script with bash, not with sh.
You are using process substitution, which is not a standard POSIX shell feature. sh is a POSIX-compatible shell, so it does not support language extensions like process substitution. Bash will run with POSIX compatibility enabled if it is invoked as sh.
Therefore, you should execute scripts that require Bash-specific features using bash.
You clearly seem to be using bash, but for anyone reading this that needs to use a shell without support for process substitution, you can use the following:
# Instead of diff <(./myProgram) <(./otherProgram)
# A pair of named pipes to avoid using disk space
# for the output of myProgram and otherProgram
mkfifo myProgram.output
mkfifo otherProgram.output
./myProgram > myProgram.output &
./otherProgram > otherProgram.output &
diff myProgram.output otherProgram.output
rm myProgram.output otherProgram.output
This is nearly identical to how bash might perform process substitution on some platforms.
I have tried a lot but couldn't get the solution out of it. I have a simple script:
#! /bin/sh
o="12345"
a=o
b=${!a}
echo ${a}
echo ${b}
When executed like
$ . scp.sh
it produces the correct output with no errors, but when executed like:
$ ./scp.sh
it produces
./scp.sh: 4: ./scp.sh: Bad substitution
Any ideas why this is happening.
I was suggested to use bash mode and it works fine. But when I execute this same script through Python (changing the script header to bash), I am getting the same error.
I'm calling it from Python as:
import os
os.system(". ./scp.sh")
Try using:
#!/bin/bash
instead of
#! /bin/sh
The reason for this error is that two different shells are used in these cases.
$ . scp.sh command will use the current shell (bash) to execute the script (without forking a sub shell).
$ ./scp.sh command will use the shell specified in that hashbang line of your script. And in your case, it's either sh or dash.
The easiest way out of it is replacing the first line with #!/bin/bash (or whatever path bash is in).