Awk is my favorite CLI program for parsing different input. In most cases I just use it to cut out different fields from some output as its superior to cut utility – it allows me to set custom, multi-char field separator instead of just single character in cut.<\/p>\n
{} – block executed once for each line of the input.<\/p>\n
BEGIN{} – block executed\u00a0 once at the start. useful to set some variables like custom field separator FS. You could set FS in the normal block {} also… but its faster if you don’t need to do it once for each line of the input.<\/p>\n
END{} – block executed once in the end. useful to print out statistics if you count something.<\/p>\n
FS<\/strong> – input field separator. default is any amount of whitespace – one or more spaces or tabs.<\/p>\n OFS<\/strong> – output field separator, defaults to space<\/p>\n # awk print out last field using separator “.”<\/p>\n # awk print out last but one field using separator “.”. This is also useful to remove file extension from list of files.<\/p>\n # awk – print fields 1-3 only from matching line using separator “:”. Simplified version using grep below.<\/p>\n # find all unique file extensions<\/p>\n Following example queries information about client backups from netbackup master server and parses it by using if-else statements, for-loops, arrays and array sorting<\/p>\n hostlist<\/strong> should have netbackup clients hostnames. For-loop just runs bpclimagelist command for each client and parses the output. Empty BEGIN blocks could be omitted but its my habbit to keep them.<\/p>\n\n\n parse that datafile.txt with another awk and produce report of missing backups.<\/p>\n\n\n\n to be continued…<\/p>\n\n\n\n# echo \"one.two.three\" <\/code>|awk 'BEGIN{FS=\".\"}{print $NF;}'\nthree<\/code><\/pre>\n$ echo \"one.two.three\" <\/code>|awk 'BEGIN{FS=\".\"}{X=NF-1; print $X;}'\ntwo
# remove file extension - quick and dirty solution. does not take into account files having zero or more than one . in the name.
\u00a3 find . -type f -printf '%f\\n' |awk 'BEGIN{FS=\".\"}{X=NF-1; print $X;}'<\/code><\/pre>\n# awk 'BEGIN{FS=\":\";}\/root\/{print $1 $2 $3;}'< \/etc\/passwd\nrootx0\n# grep root \/etc\/passwd| awk 'BEGIN{FS=\":\";}{print $1 $2 $3;}'\nrootx0<\/code><\/pre>\n# find \/path\/to\/files\/ -type f |awk 'BEGIN{FS=\".\";}{print $NF;}' |sort |uniq<\/code><\/pre>\nArrays, loops, conditional expressions<\/h1>\n
for h in `cat hostlist`;do\n\n\/usr\/openv\/netbackup\/bin\/bpclimagelist -client ${h} -server netbackup.masterserver.net |awk -v hostname=\"${h}\" 'BEGIN{}{if (lastincremental == \"\" && $7 == \"Incr\" && $8 == \"Backup\"){lastincremental=$1;}; if (lastfull == \"\" && $7 == \"Full\" && $8 == \"Backup\"){lastfull=$1;}; if (lastfull != \"\" && lastincremental != \"\"){exit}; }END{if (lastincremental == \"\"){lastincremental=\"n\/a\"}; if (lastfull == \"\"){lastfull=\"n\/a\"}; print hostname,\" \",lastincremental,\" \",lastfull;}' >> datafile.txt\n\ndone<\/code><\/pre>\n\n\n\ngrep \"n\/a\" datafile.txt |awk 'BEGIN{}{if($2 == \"n\/a\" && $3 == \"n\/a\" ){both[bothlen++]=$1} else if($2 == \"n\/a\"){incr[incrlen++]=$1} else if( $3 == \"n\/a\" ){full[fulllen++]=$1};}END{if (bothlen > 0){asort(both);print \"Servers without full or incremental successful backups\"; for (b = 0; b < bothlen; b++){print both[b];}; print \"\";}; if ( incrlen > 0){ asort(incr); print \"Servers without incremental successful backups\"; for (i = 0; i < incrlen; i++){print incr[i];}; print \"\";}; if ( fulllen > 0 ){ asort(full); print \"Servers without full successful backups\"; for (f = 0; f < fulllen; f++){print full[f];};}; }'<\/code><\/pre>\n\n\n\n