CODEWITHSUNDEEP
symlinkmainframezosjcl
Avi
Avi

Reputation: 33

Replacing target of symlink with newest subfolder using zOS script

Every time I deploy an agent on zOS server, a new subfolder is created under /usr/local/avi/ .

I manually change an existing symlink to that subfolder, the newest one, after each deployment.

I want to write a job that would check which is the newest subfolder under /usr/local/avi and update the symlink accordingly.

I have almost no knowledge of zOS.

Thanks

Upvotes: 0

Views: 283

Answers (1)

phunsoft
phunsoft

Reputation: 2745

By "... want to write a job...", are you talking about a z/OS batch job? If so, you can run prgram BPXBATCH to run the shell commands or shell script you would run manually on a shell session.

//jobname JOB CLASS=....  <== You need to adapt this JOB statement to fit your installations needs.
//STEP01   EXEC PGM=BPXBATCH
//STDOUT   DD   SYSOUT=*
//STDERR   DD   SYSOUT=*
//STDENV   DD   *
SYMLINK=sym-link-to-current-dir
DIRPREFIX=deployment-directory-prefix
/*
//STDPARM  DD   *
SH
  cd /target/directory ;                                         
  rm $SYMLINK ;                                             
  ln -s  $(ls -trd $DIRPREFIX* | tail -n 1)  $SYMLINK ;  
/*

Above commands assume that the name of the deployment directories have a common prefix. Adjust variable DIRPREFIX under //STDENV accordingly. For convenience, the symlink name is also set as variable (SYMLINK).

Note The shell pipe symbol | is a variant character. That means the actual character to be typed in the TSO/ISPF session depends on the code page you're using. For example, I'm running with CP500 (Multinational), and I have to type an exclamation point ! for the shell to see the |.

Running a batch job implies that you are allowed to submit the job, and that you are allowed to read the jobs output, e.g. via SDSF in your TSO/ISPF session.

There is no means to automatically detect directory creation and fire up some script, as far as I can tell.

Some details about the UNIX commands run:

  1. The cd /target/directory should be self-explanatory

  2. The rm $SYMLINK removes the symlink, so that it can be created again pointing the the new directory.

  3. The next line ln -s $(ls -trd $DIRPREFIX* | tail -n 1) $SYMLINK creates a new symlink to the newest directory. In this line, the part $(.....) runs a subshell and returns the resulting output (stdout) back to the parent shell, which replaces the $(.....) with the result, and then continues to execute the command line.

The ls -trd $DIRPREFIX* lists the names of all matching directories (*1) and sorts the output by time (-t) in reverse order (-r), so that the newest directory will be listed in the last line. This output is then piped to the tail -n 1 command which list only the last line (-n 1). This is line is then replacing the $(.....) to complete the ln utility.

(*1) Actually the ls lists all directory entries matching the $DIRPREFIX* operand, not only directories. But for the current problem, it is assumed that there are no other matching entries but (deployment) directory entries.

Upvotes: 2

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