How to tail multiple files using tail -0f in Linux/AIX

Question

I tried tailing two files using the option:

tail -0f file1.log -0f file2.log

In Linux I see an error "tail : can process only one file at a time".

In AIX I see the error as "Invalid options".

This works fine when I use:

tail -f file1 -f file 2

in Linux but not in AIX.

I want to be able to tail multiple files using -0f or -f in AIX/Linux

multitail is not recognized in either of these OS.

Answer 1

What about:

tail -f file1 & tail -f file2

Or prefixing each line with the name of the file:

tail -f file1 | sed 's/^/file1: /' &
tail -f file2 | sed 's/^/file2: /'

To follow all the files whose name match a pattern, you could implement the tail -f (which reads from the file every second continuously) with a zsh script like:

#! /bin/zsh -
zmodload zsh/stat
zmodload zsh/zselect
zmodload zsh/system
set -o extendedglob

typeset -A tracked
typeset -F SECONDS=0

pattern=${1?}; shift

drain() {
  while sysread -s 65536 -i $1 -o 1; do
    continue
  done
}

for ((t = 1; ; t++)); do
  typeset -A still_there
  still_there=()
  for file in $^@/$~pattern(#q-.NoN); do
    stat -H stat -- $file || continue
    inode=$stat[device]:$stat[inode]
    if
      (($+tracked[$inode])) ||
        { exec {fd}< $file && tracked[$inode]=$fd; }
    then
      still_there[$inode]=
    fi
  done
  for inode fd in ${(kv)tracked}; do
    drain $fd
    if ! (($+still_there[$inode])); then
      exec {fd}<&-
      unset "tracked[$inode]"
    fi
  done
  ((t <= SECONDS)) || zselect -t $((((t - SECONDS) * 100) | 0))
done

Then for instance, to follow all the text files in the current directory recursively:

that-script '**/*.txt' .

Answer 2

In OSX and Linux, using

tail -f <file1> <file2>

works great for me. Another nice thing is that it has the following output:

==> /srv/www/my-app/shared/log/nginx.access.log <==
things from log 1

==> /srv/www/my-app/shared/log/nginx.error.log <==
things from log 2

==> /srv/www/my-app/shared/log/nginx.access.log <==
new things from log 1

to help you recognize which output is from which log.

Answer 3

tail multiple files is extended by GNU tail version. With AIX, you don't have GNU tail, so you can't do it. You can use multitail instead.

You can install multitail in both Linux and AIX.

• With AIX, you can download package here.

• In Linux, multitail is often in repo, so you can install it easily using distro package manager:

  • In Debian/Ubuntu: apt-get install multitail
  • In Centos/Fedora: yum install multitail

Answer 4

The following thing works fine to output things on std out

tail -f file1 & tail -f file2

I wanted to pipe the output to another process. In above case & was making the part before it run in the background and only second part was being piped to process

so I used

tail -f file1 file2 | process

@Stéphane your answer is perfect, but just mentioning my use case which has a little twist.

Answer 5

I will provide a code snippet using tmux that can give you two different windows you can use to tail both files simultaneously:

tmux new-window -a -n Tail
tmux new-session -d -s Tail -n SSH0 -d
tmux selectp -t Tail

#This is tmux interactions with the user (colors of the tabs used, hot keys, etc.)
tmux bind-key -n M-Left previous-window -t WinSplit
tmux bind-key -n M-Right next-window -t WinSplit
tmux set-window-option -g monitor-activity on
tmux set -g visual-activity on
tmux set-window-option -g window-status-current-bg blue
tmux set-window-option -g window-status-fg red
tmux set -g pane-border-fg yellow
tmux set -g pane-active-border-bg red
tmux set -g message-fg yellow
tmux set -g message-bg red
tmux set -g message-attr bright
tmux set -g status-left "#[fg=red]#S"

#Names two seperate windows
tmux new-window -n tail1 -t Tail
tmux new-window -n tail2 -t Tail

#Now this will allow you to automatically run tail when this tmux script is run
tmux send-keys -t Tail:0 'tail -f file1.log' C-m
tmux send-keys -t Tail:1 'tail -f file2.log' C-m

UPDATE: Using screen can also attach/detach multiple sessions so you can run tail multiple times as well. I can suggest doing this:

screen -s Tail_Server1.log

Next you would want to hold CTRL+A+D to dettach without killing the sessions and then next:

screen -s Tail_Server2.log

Both will run two seperate screens, I would refer to screen --help so you can adjust it to how you want both screens to work on your terminal.

Answer 6

Following works for me on SunOS 5.10.

$ tail -f file1.log &
$ tail -f file2.log &
$ 

Both tails will run in background. The changes to files will be thrown to stdout. Moreover you can run any command in between just by hitting enter.

Answer 7

Use the following oneliner:

while true; do cat /path/to/numerous/folders/and/files/*/*.txt | grep "some filter" | tail -n 10; sleep 1; done

Every 1 second, the script will print 10 last lines of the filtered stream.

To break the loop, press CtrlC.

Answer 8

In Linux and OSX, supposed the files are in a different locations like these:

• logs/nginx/nginx-access.log
• logs/nginx/nginx-error.log
• logs/php/php-error.log
• logs/php/php-fpm-error.log

With the above logs, while inside the logs/ directory, you can use this command:

tail -f {php/php-{,fpm-}error,nginx/nginx-{access,error}}.log

Or you can use a wildcard to tail everything inside the logs/ directory

tail -f {nginx,php}/*.log