How can I store the result of a system command in a Perl variable

Question

cat test pl my  pid   5892  my  not   system  top -H -p  pid -n 1   grep myprocess   wc -l    print  not    not n     perl test pl 11 not   0     I want to capture the result i e  11 into a variable  How can I do that

User · Answer

Try using qx command  rather than backticks  To me  it s a bit better because  you can do SQL with it and not worry about escaping quotes and such  Depending on the editor and screen  my old eyes tend to miss the tiny back ticks  and it shouldn t ever have an issue with being overloaded like using angle brackets versus glob

User · Answer

Using backtick or qx helps  thanks everybody for the answers  However  I found that if you use backtick or qx  the output contains trailing newline and I need to remove that  So I used chomp    chomp  host    hostname    chomp  domain    domainname     fqdn    host      domain    More information here   http   irouble blogspot in 2011 04 perl-chomp-backticks html

User · Answer

The easiest way is to use the    feature in Perl  This will execute what is inside and return what was printed to stdout    my  pid   5892   my  var    top -H -p  pid -n 1   grep myprocess   wc -l    print  not    var n     This should do it

User · Answer

Also for eg  you can use IPC  Run  use IPC  Run qw run    my  pid   5892  run  qw top -H -n 1 -p    pid            sub   print grep    myprocess     lt STDIN gt               qw wc -l          gt     my  out   print  out    processes are running without bash subprocess can be piped to perl subs very similar to shell

User · Answer

Use backticks for system commands  which helps to store their results into Perl variables  my  pid   5892  my  not     top -H -p  pid -n 1   grep myprocess   wc -l    print  quot not    not n quot

User · Answer

From Perlfaq8   You re confusing the purpose of system   and backticks       system   runs a command and returns exit status information  as a 16 bit value  the low 7 bits are the signal the process died from  if any  and the high 8 bits are the actual exit value   Backticks      run a command and return what it sent to STDOUT    exit status     system  mail-users     output string    ls     There are many ways to execute external commands from Perl  The most commons with their meanings are    system     you want to execute a command and don t want to capture its output exec  you don t want to return to the calling perl script backticks   you want to capture the output of the command open  you want to pipe the command  as input or output  to your script   Also see How can I capture STDERR from an external command

[perl] How can I store the result of a system command in a Perl variable?

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