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Full Discussion: WHy do we need both append and output directives?
Top Forums UNIX for Beginners Questions & Answers WHy do we need both append and output directives? Post 303001570 by mojoman on Monday 7th of August 2017 01:54:16 PM
Old 08-07-2017
WHy do we need both append and output directives?
Hi,

I was reviewing a shell script and I found this line:

Code:
yum -y update >> >(/usr/bin/tee /var/log/file)

I have tried removing the >> directive and all that will occur is that the file will be created--nothing gets put in the file. If I put back the >> directive it works. If I remove the > the line fails. Why are both >> and > required?

Thanks.
 

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LEARN ABOUT OPENSOLARIS

tee

tee(1)								   User Commands							    tee(1)

NAME

       tee - replicate the standard output

SYNOPSIS

   /usr/bin/tee
       /usr/bin/tee [-ai] [file]...

   ksh93
       tee [-ail] [file]...

DESCRIPTION

   /usr/bin/tee
       /usr/bin/tee  copies  standard  input  to standard output, making a copy in zero or more files. tee does not buffer its output. The options
       determine if the specified files are overwritten or appended to.

   ksh93
       The tee built-in in ksh93 is associated with the /bin and /usr/bin paths. It is invoked when tee is executed without a pathname prefix  and
       the pathname search finds a /bin/tee or /usr/bin/tee executable.

       tee  copies  standard input to standard output and to zero or more files. The options determine whether the specified files are overwritten
       or appended to. The tee utility does not buffer output. If a write to a file fails, tee continues to write to other files although it exits
       with a non-zero exit status.

       The number of file operands that can be specified is limited by the underlying operating system.

OPTIONS

   /usr/bin/tee
       The following options are supported by /usr/bin/tee:

       -a    Appends the output to the files rather than overwriting them.

       -i    Ignores interrupts.

   ksh93
       The following options are supported by the tee built-in command in ksh93:

       -a		      Appends the output to the files rather than overwriting them.
       --append

       -i		      Ignores SIGINT signal.
       --ignore-interrupts

       -l		      Sets the standard output to be line buffered.
       --line-buffer

OPERANDS

       The following operands are supported:

       file    A path name of an output file. Processing of at least 13 file operands are supported.

USAGE

       See largefile(5) for the description of the behavior of tee when encountering files greater than or equal to 2 Gbyte ( 2^31 bytes).

ENVIRONMENT VARIABLES

       See  environ(5)	for  descriptions of the following environment variables that affect the execution of tee: LANG, LC_ALL, LC_CTYPE, LC_MES-
       SAGES, and NLSPATH.

EXIT STATUS

   /usr/bin/tee
       The following exit values are returned by /usr/bin/tee:

       0     The standard input was successfully copied to all output files.

       >0    The number of files that could not be opened or whose status could not be obtained.

   ksh93
       The following exit values are returned by tee in ksh93:

       0     Successful completion.

       >0    An error occurred.

ATTRIBUTES

       See attributes(5) for descriptions of the following attributes:

   /usr/bin/tee
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |CSI			     |Enabled			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |Committed 		   |
       +-----------------------------+-----------------------------+
       |Standard		     |See standards(5). 	   |
       +-----------------------------+-----------------------------+

   ksh93
       +-----------------------------+-----------------------------+
       |      ATTRIBUTE TYPE	     |	    ATTRIBUTE VALUE	   |
       +-----------------------------+-----------------------------+
       |Availability		     |SUNWcsu			   |
       +-----------------------------+-----------------------------+
       |Interface Stability	     |See below.		   |
       +-----------------------------+-----------------------------+

       The ksh93 built-in binding to /bin and /usr/bin is Volatile. The built-in interfaces are Uncommitted.

SEE ALSO

       cat(1), ksh93(1), attributes(5), environ(5), largefile(5), standards(5)

SunOS 5.11							    20 Nov 2007 							    tee(1)
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