What does this command do (strange assignments and redirections)

Question

I would like to get more details on what the below command is doing:

PASSING=0 FAILED=0 > log_${ENV} print "Test Started at `date`\n"

Answer 1

The command may be rewritten as

PASSING=0 FAILED=0 print "Test Started at `date`\n" >log_${ENV}

as the redirection may occur at any point on the command line.

The redirection sends the output of the print command to the file named log_${ENV} (or log_$ENV, the curly braces won't do anything here), where ENV is supposedly a shell variable with some value that exists in the current environment.

The two assignments to PASSING and FAILED will set these two variables in the environment of the print command. They will not exist after the execution of this line (unless they existed before in the script, in which case their original values would remain unmodified after execution of this command line).

Since print does not seem like it's using these two variables (unless it's a script or a function or something else that we don't know about), it's difficult to say what the intention is with the variables.

The print thing takes a text string as its only argument, where a part of the string is an old-styled command substitution that will expand to the output of the date command before print is invoked. Using a more modern command substitution syntax, the argument could also be written as "Test Started at $(date)\n".

The overall effect would probably (depending on what print does) be to write the given text string into a specific file whose name depends on the value $ENV.

Related:

• Why is setting a variable before a command legal in bash?
• How is this command legal ? "> file1 < file2 cat"
• Have backticks (i.e. `cmd`) in *sh shells been deprecated?

---

In ksh93 (and zsh), print is a shell built-in utility that acts (loosely speaking) a bit like echo. That shell also treats $ENV in a special way in that it will source the file that $ENV points to when starting an interactive shell. Using it (or upper-case variables in general) as a generic variable in a shell script is not advised.

Related to this:

• Are there naming conventions for variables in shell scripts?

Answer 2

You have to "parse" (interpret) the command line (divide into words):

PASSING=0 FAILED=0 >log_${ENV} print "Test Started at `date`\n"
\___  __/ \__  __/ \___  ____/ \_ _/  \_________  ____________/
    \/       \/        \/        \/             \/
   var1     var2    redirect    cmd    "Argument to command".

Those are the five words (divided on spaces) that make up the command line.

• A var before a command, like in var=123 cmd will be defined in the environment for (only) the duration of the command execution. Then, it will be discarded.

  Several variables could be defined before the command name.

• A redirection is used to send output to a file or read input from a file. A redirection could appear at any place of the command line and will be applied for the whole command line (command execution).

  In this case, the redirection is to output to a file called as the concatenation of the word log_ and the value inside the variable ENV (the $(ENV) part).

• Obviously, the command name print in this case.

  This command name exists (as builtin) in ksh, mksh,lksh and zsh, but not in ash, dash, csh, yash, bash (and others). In those shells, the command may exist as an external program to be found in the PATH.

• Argument(s) is the list of parameters, text, or other information that is given to the command and available in c programs as argv[] and int argc or in shell as $@ and $#.

  In this case, the argument include one command expansion `date`, equivalent to (in modern syntax and strongly recommended) $(date). That part will execute the command (in this case) date and will replace the whole part with the output of the command. In short: will place the actual date at that place.

The whole command could also be written (to the exact same effect) as:

PASSING=0 FAILED=0   print "Test Started at `date`\n"     >log_${ENV}

Which, not having enough information, seems to be printing one string into a log file. If it is indeed the built-in print mentioned above, the two variables will have no effect and could be erased to write the command as :

print "Test Started at `date`\n"     >log_${ENV}

But that is just an educated guess, to actually know what is the print command doing, you need to dig a little deeper. You need to say which shell is running the command and (if valid for your shell), the output of type print.