Syntax Error in Shell Script With Process Substitution

Syntax error in shell script with process substitution

The syntax you've used is a bash extension to the basic shell syntax, so you must take care to run your script with bash. (Ksh also has >(…) process substitution but doesn't support it after a redirection. Zsh would be fine.)

Given the error message you're getting, you are running this script in bash, but in its POSIX compatibility mode, not in full bash mode. Take care to invoke your script with an explicit #!/bin/bash line. #!/bin/sh won't do, even if /bin/sh is a symbolic link to bash, because bash runs in POSIX mode if it's invoked under the name sh. Always invoke bash by name if you use bash features.

Also take care not to set the environment variable POSIXLY_CORRECT or to pass the --posix option on the command line if you want to use bash features.

Alternatively, don't use this bash-specific syntax; use a portable construct such as the one proposed by Stephane Rouberol.

Why does process substitution not work in a shell script?

It isn't entirely clear yet, but the chances are very high that you either have an incorrect shebang line at the top of the script:

#!/bin/sh

or you are using sh script.sh instead of bash script.sh while testing it, or you have SHELL=/bin/sh or something similar set in the environment. Your failure is on the process substitution code. When Bash is run as sh (in POSIX mode), then process substitution is not available:

30. Process substitution is not available.

You need to write:

#!/bin/bash

temp=$(comm -12 <(sort -u /home/xyz/a.csv1) <(sort -u /home/abc/tempfile) | wc -l)
echo $temp

or even simply:

#!/bin/bash

comm -12 <(sort -u /home/xyz/a.csv1) <(sort -u /home/abc/tempfile) | wc -l

which will achieve the same effect as the capture followed by the echo. When testing, use bash -x script.sh or bash script.sh.

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Deciphering the indecipherable comment

In an indecipherable comment, the information appears to include:

BASH=/bin/sh

BASHOPTS=cmdhist:extquote:force_fignore:hostcomplete:interactive_comments:progco‌mp:promptvars:sourcepath

BASH_ALIASES=()

BASH_ARGC=()

BASH_ARGV=()

BASH_CMDS=()

BASH_LINENO=([0]="0")

BASH_SOURCE=([0]="a.sh")

BASH_VERSINFO=([0]="4" [1]="1" [2]="2" [3]="1" [4]="release" [5]="x86_64-redhat-linux-gnu")

BASH_VERSION='4.1.2(1)-release'

CVS_RSH=ssh

SHELL=/bin/bash

SHELLOPTS=braceexpand:hashall:interactive-comments:posix

SHLVL=2

Note that BASH=/bin/sh and SHELLOPTS=braceexpand:hashall:interactive-comments:posix. Either or both of these might be a major part of the problem.

Bash script process substitution Syntax error: ( unexpected

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

command substitution: line 72: syntax error near unexpected token `('

Supposing that the first of these lines ...

updated_run_names=$(comm -23 <(echo ${current_run_names} | tr " " "\n" | sort) <(echo ${started_run_names} | tr " " "\n" | sort) )
update_run_names=$(echo ${new_run_names} | cut -d' ' -f1)

... is the line 72 referenced in the error message, the issue is most likely with your process substitutions. These are the two fragments of the form <( command ).

Process substitution is a Bash extension to the POSIX shell language. It is not recognized by most other shells, and it is not recognized by Bash itself when it runs in POSIX mode. There is more than one way to get Bash running in POSIX mode, but one of them is to invoke it via the name sh, which is what you are doing.

Note well that the shebang line at the top of your script has a functional role only when you launch the script directly, by making it executable and launching it by name:

./conversion.sh -r directory_location

When you instead launch it as shown in the question, by naming it as an argument to sh, the shebang line is just a comment, and Bash runs (as sh) in POSIX mode.

Note also that although it is conventional for some other language interpreters (Python, especially), it is not conventional to use env in shell script shebang lines.

bash/zsh input process substitution gives syntax error in conjunction with while

You need to redirect the process substitution into the while loop:

You wrote

while read line; do echo $line; done <(cat foo)

You need

while read line; do echo $line; done < <(cat foo)
# ...................................^

Treat a process substitution like a filename.

syntax error near unexpected token `(' error with process substitution

Try using sudo:

• sudo sort test.tsv > text1.tsv
• sudo sort test2.tsv > text2.tsv
• sudo comm -13 text1.tsv text2.tsv

process substitution not working in bash script

Process substitution does not work when bash is in POSIX mode. Please disable POSIX and try again.

To disable: This will cause process substitution to work .

set +o posix

To enable: : This will cause process substitution not to work.

set -o posix

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