DTail usage examples

From ee75979b5d94ae18f930ff91e5b2d51cd554b60d Mon Sep 17 00:00:00 2001 From: Paul Buetow Date: Mon, 9 Mar 2026 22:45:54 +0200 Subject: Update content for html --- gemfeed/2023-09-25-dtail-usage-examples.html | 121 +++++++++++++-------------- 1 file changed, 58 insertions(+), 63 deletions(-) (limited to 'gemfeed/2023-09-25-dtail-usage-examples.html') diff --git a/gemfeed/2023-09-25-dtail-usage-examples.html b/gemfeed/2023-09-25-dtail-usage-examples.html index 84513d63..6723a770 100644 --- a/gemfeed/2023-09-25-dtail-usage-examples.html +++ b/gemfeed/2023-09-25-dtail-usage-examples.html @@ -2,17 +2,12 @@ - DTail usage examples -
@@ -75,7 +70,7 @@ by Lorenzo Bettini http://www.lorenzobettini.it http://www.gnu.org/software/src-highlite --> -
% dtail --servers serverlist.txt --grep INFO --files "/var/log/dserver/*.log"
+% dtail --servers serverlist.txt --grep INFO --files "/var/log/dserver/*.log"
 
 

 Hint: you can also provide a comma separated server list, e.g.: servers server1.example.org,server2.example.org:PORT,...

@@ -88,7 +83,7 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dtail --servers serverlist.txt --grep INFO "/var/log/dserver/*.log"
+% dtail --servers serverlist.txt --grep INFO "/var/log/dserver/*.log"
 
 

 Aggregating logs


@@ -101,10 +96,10 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dtail --servers serverlist.txt \
-    --files '/var/log/dserver/*.log' \
-    --query 'from STATS select sum($goroutines),sum($cgocalls),
-             last($time),max(lifetimeConnections)'
+% dtail --servers serverlist.txt \
+    --files '/var/log/dserver/*.log' \
+    --query 'from STATS select sum($goroutines),sum($cgocalls),
+             last($time),max(lifetimeConnections)'
 
 

 Beware: For map-reduce queries to work, you have to ensure that DTail supports your log format. Check out the documentaiton of the DTail query language and the DTail log formats on the DTail homepage for more information.

@@ -117,10 +112,10 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dtail --servers serverlist.txt \
-    --files '/var/log/dserver/*.log' \
-    'from STATS select sum($goroutines),sum($cgocalls),
-     last($time),max(lifetimeConnections)'
+% dtail --servers serverlist.txt \
+    --files '/var/log/dserver/*.log' \
+    'from STATS select sum($goroutines),sum($cgocalls),
+     last($time),max(lifetimeConnections)'
 
 

 Here is another example:

@@ -129,10 +124,10 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dtail --servers serverlist.txt \
-    --files '/var/log/dserver/*.log' \
-    --query 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
-             lifetimeConnections group by $hostname order by max($cgocalls)'
+% dtail --servers serverlist.txt \
+    --files '/var/log/dserver/*.log' \
+    --query 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
+             lifetimeConnections group by $hostname order by max($cgocalls)'
 
 

 

@@ -143,9 +138,9 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dtail --servers serverlist.txt \
-    --files '/var/log/dserver/*.log' \
-    --query 'from STATS select ... outfile append result.csv'
+% dtail --servers serverlist.txt \
+    --files '/var/log/dserver/*.log' \
+    --query 'from STATS select ... outfile append result.csv'
 
 

 How to use dcat


@@ -158,7 +153,7 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dcat --servers serverlist.txt --files /etc/hostname
+% dcat --servers serverlist.txt --files /etc/hostname
 
 

 

@@ -169,7 +164,7 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dcat --servers serverlist.txt /etc/hostname
+% dcat --servers serverlist.txt /etc/hostname
 
 

 How to use dgrep


@@ -180,9 +175,9 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dgrep --servers server1.example.org:2223 \
-    --files /etc/passwd \
-    --regex nologin
+% dgrep --servers server1.example.org:2223 \
+    --files /etc/passwd \
+    --regex nologin
 
 

 Generally, dgrep is also a very useful way to search historic application logs for certain content.

@@ -199,10 +194,10 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dmap --servers serverlist.txt \
-    --files '/var/log/dserver/*.log' \
-    --query 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
-             lifetimeConnections group by $hostname order by max($cgocalls)'
+% dmap --servers serverlist.txt \
+    --files '/var/log/dserver/*.log' \
+    --query 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
+             lifetimeConnections group by $hostname order by max($cgocalls)'
 
 

 Remember: For that to work, you have to make sure that DTail supports your log format. You can either use the ones already defined in internal/mapr/logformat or add an extension to support a custom log format. The example here works out of the box though, as DTail understands its own log format already. 

@@ -225,9 +220,9 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dmap --files /var/log/dserver/dserver.log
-    --query 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
-              lifetimeConnections group by $hostname order by max($cgocalls)'
+% dmap --files /var/log/dserver/dserver.log
+    --query 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
+              lifetimeConnections group by $hostname order by max($cgocalls)'
 
 

 As a shorthand version the following command can be used:

@@ -236,9 +231,9 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dmap 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
-        lifetimeConnections group by $hostname order by max($cgocalls)' \
-        /var/log/dsever/dserver.log
+% dmap 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
+        lifetimeConnections group by $hostname order by max($cgocalls)' \
+        /var/log/dsever/dserver.log
 
 

 You can also use a file input pipe as follows:

@@ -247,9 +242,9 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% cat /var/log/dserver/dserver.log | \
-    dmap 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
-          lifetimeConnections group by $hostname order by max($cgocalls)'
+% cat /var/log/dserver/dserver.log | \
+    dmap 'from STATS select $hostname,max($goroutines),max($cgocalls),$loadavg,
+          lifetimeConnections group by $hostname order by max($cgocalls)'
 
 

 Aggregating CSV files


@@ -260,16 +255,16 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% cat example.csv
-name,lastname,age,profession
-Michael,Jordan,40,Basketball player
-Michael,Jackson,100,Singer
-Albert,Einstein,200,Physician
-% dmap --query 'select lastname,name where age > 40 logformat csv outfile result.csv' example.csv
-% cat result.csv
-lastname,name
-Jackson,Michael
-Einstein,Albert
+% cat example.csv
+name,lastname,age,profession
+Michael,Jordan,40,Basketball player
+Michael,Jackson,100,Singer
+Albert,Einstein,200,Physician
+% dmap --query 'select lastname,name where age > 40 logformat csv outfile result.csv' example.csv
+% cat result.csv
+lastname,name
+Jackson,Michael
+Einstein,Albert
 
 

 DMap can also be used to query and aggregate CSV files from remote servers.

@@ -282,44 +277,44 @@ http://www.gnu.org/software/src-highlite -->
 by Lorenzo Bettini
 http://www.lorenzobettini.it
 http://www.gnu.org/software/src-highlite -->
-% dtail /var/log/dserver/dserver.log
+% dtail /var/log/dserver/dserver.log
 
 

 
-% dtail --logLevel trace /var/log/dserver/dserver.log
+% dtail --logLevel trace /var/log/dserver/dserver.log
 
 

 
-% dcat /etc/passwd
+% dcat /etc/passwd
 
 

 
-% dcat --plain /etc/passwd > /etc/test
-# Should show no differences.
-diff /etc/test /etc/passwd 
+% dcat --plain /etc/passwd > /etc/test
+# Should show no differences.
+diff /etc/test /etc/passwd 
 
 

 
-% dgrep --regex ERROR --files /var/log/dserver/dsever.log
+% dgrep --regex ERROR --files /var/log/dserver/dsever.log
 
 

 
-% dgrep --before 10 --after 10 --max 10 --grep ERROR /var/log/dserver/dsever.log
+% dgrep --before 10 --after 10 --max 10 --grep ERROR /var/log/dserver/dsever.log
 
 

 Use --help for more available options. Or go to the DTail page for more information! Hope you find DTail useful!

@@ -339,11 +334,11 @@ http://www.gnu.org/software/src-highlite -->
 

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