202202 SUGUKI UNIX X Command Tips and Tricks

David B. Horvath, CCP, MS
February 2022 SUGUKI
UNIX X Command Tips and Tricks

Presenter
The Author can be contacted at:
504 Longbotham Drive, Aston PA 19014-2502,
USA
Phone: +1-610-859-8826
Email: dhorvath@cobs.com
Web: http://www.cobs.com/
LI: http://www.linkedin.com/in/dbhorvath
David B. Horvath, CCP, MS
Copyright © 2019 - 2022 David B. Horvath, CCP — All Rights
Reserved

Abstract
SAS provides the ability to execute operating system level commands from within your SAS
code – generically known as the “X Command”. This session explores the various commands,
the advantages and disadvantages of each, and their alternatives. The focus is on UNIX/Linux
but much of the same applies to Windows as well. Under SAS EG, any issued commands
execute on the SAS engine, not necessarily on the PC.
 X
 %sysexec
 Call system
 Systask command
 Filename pipe
 &SYSRC
 Waitfor
Alternatives will also be addressed – how to handle when NOXCMD is the default for your
installation, saving results, and error checking.

My Background
 David is an IT Professional who has worked with various platforms since the
1980’s with a variety of development and analysis tools.
 He has presented at PhilaSUG, SESUG, and SGF previously and has presented
workshops and seminars in Australia, France, the US, Canada, and Oxford
England (about the British Author Nevil Shute).
 He holds an undergraduate degree in Computer and Information Sciences from
Temple University and a Masters in Organizational Dynamics from UPENN. He
achieved the Certified Computing Professional designation with honors.
 Most of his career has been in consulting (although recently he has been in-
house) in the Philadelphia PA area. He is currently in Data Analytics
"Engineering" at a Regional Bank.
 He has several books to his credit (none SAS related) and is an Adjunct Instructor
covering IT topics.

Options
 Execution of any System command from within your SAS program is dependent
on one option's setting:
XCMD Enables the X command in SAS.
 Which can only be set at startup:
options xcmd;
____
30
WARNING 30-12: SAS option XCMD is valid only at startup of the SAS
System. The SAS option is ignored.
 If NOXCMD is set, you're out of luck. Sorry!
 University Edition is NOXCMD

X
 The basic X Command
 Runs independent of data steps and macros
 The SAS Engine will interpret some commands
 Does not spawn off sub-process
 This fact is important because information does not persist between sub-
processes
 Handling within the log is annoying

X
 X Command Examples:
 pwd and cd under UNIX:
NOTE: Current working directory is
'/this/is/the/sas/install/directory'.
26 x "pwd" ; /* works within SAS */
27 x "cd /my/directory/is/here"
27 ! ; /* works within SAS */
NOTE: Current working directory is '/my/directory/is/here'.
28 x "pwd" ; /* works within SAS */
 echo and combined commands under UNIX:
29 x "echo $HOME"
29 ! ; /* works but no output */
30 x "pwd; cd $HOME; pwd"
30 ! ; /* no output, works? */

X
 We can combine commands on one line under UNIX:
31 x 'echo start; echo mid; echo end>temp2.txt'
31 ! ; /* output to file, works */
 > sends STDOUT to a file
 I know this works because I can look at the output file (temp2.txt):
end
 Why didn't "start" and "mid" appear?
 Because of the way I wrote the statement!

X
 We can combine commands on one line under UNIX:
37 x '(echo start; echo mid; echo end)>temp1.txt'
37 ! /* output to file, all 3 statements to file */
 I know this works because I can look at the output file (temp1.txt):
start
mid
end
 The difference is the parenthesis which combines the output in UNIX
 Because of the way I wrote the statement!

X and %SYSRC
 How do I know a command worked?
 %SYSRC will tell me – returns the UNIX error code
37 x '(echo start; echo mid; echo end)>temp1.txt'
37 ! ; /* output to file, all 3 statements to file */
SYMBOLGEN: Macro variable SYSRC resolves to 0
38 %put &SYSRC;
0
 Zero is success in UNIX

X and %SYSRC
 If the command does not exist, we get 127:
41 x 'this_command_doesnot_exist 2>test5.txt'
41 ! ; /* non-zero RC */
42 %put &SYSRC;
127
 And we can save error output (2> sends STDERR to a file):
/bin/bash: this_command_doesnot_exist: command not found
43 x 'ls -al no_such_file'
43 ! ; /* non-zero RC */
44 %put &SYSRC;
2

X and %SYSRC
 The command itself may return an error as well:
43 x 'ls -al no_such_file'
43 ! ; /* non-zero RC */
44 %put &SYSRC;
2
 In this case, "no_such_file" does not exist
 'man ls' executed at the command line will provide this information
Exit status:
0 if OK,
1 if minor problems (e.g., cannot access subdirectory),
2 if serious trouble (e.g., cannot access command-line argument).

%sysexec – Macros
 We can execute system commands within a macro:
72 %macro commands;
73 %sysexec %str(ls -al > test6.txt);
74 %put &SYSRC;
75 %sysexec %str(command_doesnot_exist 2> test7.txt);
76 %put &SYSRC;
77 %mend commands;
78
79 %commands;
 Note the use of %SYSRC

%sysexec – Macros
 And get the following results:
79 %commands;
MLOGIC(COMMANDS): Beginning execution.
MLOGIC(COMMANDS): %SYSEXEC ls al test6.txt
MLOGIC(COMMANDS): %PUT &SYSRC
0
MLOGIC(COMMANDS): %SYSEXEC command_doesnot_exist 2 test7.txt
MLOGIC(COMMANDS): %PUT &SYSRC
127
MLOGIC(COMMANDS): Ending execution.

Call System – Data Step
 Use Call System within a data step:
85 data dir;
86 filename commands PIPE "ls | head -2";
87 infile commands truncover;
88 input result $char60.;
89
90 string="echo " || result || " >> test4.txt";
91 call system(string); /* no output - but it executes multiple
times */
92 system_rc=symget("SYSRC");
93 call system("this_command_doesnot_exist");
94 system_rc2=symget("SYSRC");
95
96 systask command "pwd" wait shell; /* runs once */
NOTE: LOG/Output from task "task59"
> /my/directory/is/here
NOTE: End of LOG/Output from task "task59"
97 output;
98 run;

 Call System results:
NOTE: The infile COMMANDS is:
Pipe command="ls | head -2"
NOTE: 2 records were read from the infile COMMANDS.
The minimum record length was 22.
The maximum record length was 24.
NOTE: The data set WORK.DIR has 2 observations and 4
variables.
NOTE: Compressing data set WORK.DIR increased size by 100.00
percent.
Compressed is 2 pages; un-compressed would require 1
pages.
NOTE: DATA statement used (Total process time):
real time 0.02 seconds
cpu time 0.00 seconds

 Call System output:
 Results:
 Test4.txt:
FILE1
FILE2
 Two records were read from infile
 Two records were written to work.dir
 Two records were written to test4.txt via the echo command
 SAS Engine does not interpret these commands
Obs result string system_rc system_rc2
1FILE1 echo FILE1 >> test4.txt 0 127
2FILE2 echo FILE2 >> test4.txt 0 127

'Systask command'
 'Systask command' operates two modes:
 With "shell" modifier, SAS does not interpret the commands
 Without "shell", it behaves like X
 &SYSRC is set
54 systask command 'echo BOL $HOME EOL' wait;
> BOL $HOME EOL
54 ! /* $HOME not interpreted */
55 systask command "echo BOL $HOME EOL" wait shell;
> BOL /my/directory/is/here EOL
55 ! /* $HOME interpreted */

'Systask command' and 'Systask list'
 Other Options:
 Wait: wait for this command to execute before starting next
 Cleanup: wait for this command and any nowait before starting next
 Shell: Can also specify the shell to use: shell="/usr/bin/ksh"
 Status: Can specify a status variable to check later (rather than &SYSRC)
 Taskname: Can specify task name for later use in Waitfor
 Systask list will provide status of any nowait systasks
"task150" --------------
Type: Task
State: COMPLETE
Status Macro Variable: Unspecified
73
74 systask list;

'Systask command' and 'Waitfor'
 The waitfor command is used to wait for systask command nowait to
complete
 Can wait for _ANY_ of listed tasknames to complete (default)
 Can wait for _ALL_ of listed tasknames to complete
 Can specify length of time to wait: Timeout=number-of-seconds
 General form is
waitfor _ALL_ task1 task2 task3;

Filename pipe
 Acts like normal filename statement
 Accepts data written from SAS (File/Put)
 Provides data for SAS to read (Infile/Input)
 Allows for execution of UNIX command
 Is more efficient than running command separately (parallelization)
 Handy when you have version limitations:
filename gzipit zip '/my/output/directory/file.txt.gz' gzip; *
requires 9.4M5;
filename gzipit pipe 'gzip -c >
/my/output/directory/file.txt.gz'; * run the UNIX gzip;

Filename Pipe – Earlier Code Example
 UNIX Commands are Executed prior to input statement:
85 data dir;
86 filename commands PIPE "ls | head -2";
89
90 string="echo " || result || " >> test4.txt";
91 call system(string); /* no output - but it executes multiple
times */
93 call system("this_command_doesnot_exist");
94 system_rc2=symget("SYSRC");
95
96 systask command "pwd" wait shell; /* runs once */
> /my/directory/is/here
97 output;
98 run;

Filename Pipe
 Unfortunately, &SYSRC is not set by Filename Pipe:
113 data baddir;
114 filename commands PIPE "lx ; lx ; lx";
116
119 output;
120 run;
NOTE: The infile COMMANDS is:
Pipe command="lx ; lx ; lx"
NOTE: 3 records were read from the infile COMMANDS.
The minimum record length was 32.
The maximum record length was 32.

Shell Scripts
 When NOXCMD is set, none of these will work.
 You can move the commands into a shell script:
#!/bin/ksh
cd /desired/directory
# You can check return codes here with the $?
if [[ $? -gt 0 ]]; then
echo "cd failed"
exit 3
fi
# if we get here 'cd' succeeded
ls –al | head -2 > temp.txt
sas your_sas_part_1.sas
pwd
sas your_sas_part_2.sas
gzip /my/output/directory/file.txt

Final Thoughts
 It is all about choices
 Sometimes it is better to execute UNIX commands in your program
 Sometimes not

Wrap Up
Questions
and
Answers
?!
?!
?!
?!
?
?
?
?
! !
! !

Named Pipes under UNIX –
Filename Pipe with NOXCMD
 I can use UNIX “Named Pipes” with files
 Datasets make use of the "Sequential Data Engine" ("TAPE" engine)
 External Command Example – Write:
 UNIX/Linux commands:
mknod mypipe p
gzip –c mypipe > input.gz & /* runs in background */
sas writepipe.sas
 writepipe.sas Program:
libname test "mypipe";
data test.test_no (compress=no drop=text1-text44) ;
array text[44] $20 (/* list of 44 words or phrases */);
format longstring $200. ;
DO indexvariable=1 TO 20000000;
/* create a bunch of random values */
output test.test_no;
END;
run;

Named Pipes under UNIX –
Filename Pipe with NOXCMD
 External Command Example – Read:
 UNIX/Linux commands:
mknod mypipe p /* not needed if created before)
gzip –-stdout input.gz > mypipe & /* runs in background/parallel */
sas readpipe.sas
 readpipe.sas Program:
libname test "mypipe";
data _null_;
set test.test_no;
retain total 0;
total=total+num1;
run;

UNIX X Command Tips and Tricks
 The Author can be contacted at:
David B. Horvath, CCP
504 Longbotham Drive, Aston PA 19014-2502, USA
Phone: +1-610-859-8826
Email: dhorvath@cobs.com
Web: http://www.cobs.com/
LI: http://www.linkedin.com/in/dbhorvath

References
 x, sysexc, system:
 http://support.sas.com/documentation/cdl/en/hostunx/61879/HTML/default/viewer.htm#xcomm.htm
 http://support.sas.com/documentation/cdl/en/hostunx/63053/HTML/default/viewer.htm#p0w085btd5r0a4n1km4bcdpgqibt.htm
 %sysexec:
 http://support.sas.com/documentation/cdl/en/mcrolref/62978/HTML/default/viewer.htm#n08ecabbpebv2xn13ieu8uylrohm.htm
 filename pipe:
 http://support.sas.com/documentation/cdl/en/hostunx/63053/HTML/default/viewer.htm#n1ceb0xedanuj3n19l3g73awk1wf.htm
 https://documentation.sas.com/?docsetId=hostunx&docsetTarget=n1ceb0xedanuj3n19l3g73awk1wf.htm&docsetVersion=9.4&lo
cale=en
 bash scripts:
 https://www.taniarascia.com/how-to-create-and-use-bash-scripts/
 systask:
 http://support.sas.com/documentation/cdl/en/hostunx/63053/HTML/default/viewer.htm#p0lzxl2mwndagun1dtxbst9s4jea.htm

References
 xsync:
 https://documentation.sas.com/?docsetId=hostunx&docsetTarget=p0is4umpbeej5pn
1xwc8mwgt9qz5.htm&docsetVersion=9.4&locale=en
 xcmd:
 http://support.sas.com/documentation/cdl/en/hostwin/69955/HTML/default/viewer.ht
m#p0xtd57b40ehdfn1jyk8yxemfrtv.htm
 x command (x windows) options:
 https://documentation.sas.com/?docsetId=hostunx&docsetTarget=n1nx651zrt6pdcn1
71xjr3xwfxhq.htm&docsetVersion=9.4&locale=en
 waitfor:
 https://documentation.sas.com/?docsetId=hostunx&docsetTarget=p0w8zwo1dyssdfn
1mjm11dt2v7e2.htm&docsetVersion=9.4&locale=en

Wrap Up (For Real)
Questions
and
Answers
?!
?!
?!
?!
?
?
?
?
! !
! !

202202 SUGUKI UNIX X Command Tips and Tricks

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