Hi Monks,

programming since very long and knowing quite a number of languages (like C/C++, python, java, javascript, ...), I am however very new to perl. The need for püerl came form a quite complex bash script which needs also some data mangling. I started with awk (as usually) but came to one point where AWK became very heavy to handle it. So I wanted to give perl a try.

The script (in this part) needs to analyze SYSLOG logs. With the help of goole and some tutorials I came up with:

perl -n -e "
/^(([a-zA-Z]+\s+[0-9]+\s+[0-9]+[:][0-9]+[:][0-9]+)\s+([0-9a-zA-Z-]+)\s
++([^:[]+)(\[.*?\])?\s*[:]\s*(?:([^:]*)[:])?\s*(.*))\$/ && ( \$m=(\$1,
+\$2,\$3,\$4,\$5,\$6,\$7) )  && print \$3
" "$SYSLOG"

[download]

which works fine for testing and printing the system name of each syslog record. But the script is to be more complex (actually it is a bash library function), so I need to filter. Also as a test I did then:

perl -n -e "
/^(([a-zA-Z]+\s+[0-9]+\s+[0-9]+[:][0-9]+[:][0-9]+)\s+([0-9a-zA-Z-]+)\s
++([^:[]+)(\[.*?\])?\s*[:]\s*(?:([^:]*)[:])?\s*(.*))\$/ && ( $3 =~ /^s
+ystemname$/) && print \$3
" "$SYSLOG"

[download]

But this does not work. I understand that this is because $3 is overwritten by this new regex testing. So I tryed to assign to a variable like:

perl -n -e "
/^(([a-zA-Z]+\s+[0-9]+\s+[0-9]+[:][0-9]+[:][0-9]+)\s+([0-9a-zA-Z-]+)\s
++([^:[]+)(\[.*?\])?\s*[:]\s*(?:([^:]*)[:])?\s*(.*))\$/ && ( \$m=(\$1,
+\$2,\$3,\$4,\$5,\$6,\$7) )  && ( $3 =~ /^systemname$/) && print \$m[3
+]" "$SYSLOG"

[download]

but get only empty lines as well.

Questions:

  1. am I understanding correctly that this scrip timplicitely doe s$_ =~ before the initial regex ?
  2. do I really need the first capturing group for the full line if I also need to acces the full line ($_ seems not to wrok) ?
  3. How do I access the groups of the first regex at the end print ?

Even if you think there is a better way, I do also want to understand why this way does not work as expected. In the final script there will be dynamic testing (so there can be additonal && ( $x =~....) &&

Many thanka,
Gaston

In reply to Need advice in for perl use as awk replacement by Anonymous Monk

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