How do I save command output with logsave

preface

What would you do if you wanted to save the output of a command to a file?

One common method is to use IO redirects

ls >/tmp/ls.txt 2>&1

We can use the tee command if we need to save the output of the command to a file and also output the content to the screen

ls |tee /tmp/ls.txt

Today, however, I found an logsave command that also saves command output to a file and outputs content pages to the screen.

The grammar of logsave is very simple:

logsave [ -asv ] logfile cmd_prog [args ... ]

options

-ES23en: Appends information to the specified log file.

parameter

Log file: Specifies the log file that records the operation information; Instruction: An instruction that needs to be executed.

logsave will execute cmd_prog args... And saves a copy of the command output to logfile, which is great because even if the directory logfile is in doesn't exist, logsave will save the output to memory and write it to the log file after the directory logfile is in is established

This feature of logsave makes it ideal for system startup scripts, where output is stored in memory until the /var/ directory is mounted before being written to /var/log/

Take the following example

#  Delete store logfile The directory where the 
rm -rf /tmp/logdir
#  use logsave save logfile
logsave /tmp/logdir/logfile bash -c "sleep 2;date"
#  create logdir
mkdir /tmp/logdir
echo  To view logfile Whether to generate :
ls -l /tmp/logdir
echo  Waiting for the 2s after :
sleep 2
echo  Look again at logfile Whether to generate :
ls -l /tmp/logdir
echo  To view logfile The content of the :
cat /tmp/logdir/logfile

2018 years  05 month  14 day   week 1 16:31:44 CST
 To view logfile Whether to generate :
 The total amount  0
 Waiting for the 2s after :
 Look again at logfile Whether to generate :
 The total amount  4
-rw-r--r-- 1 lujun9972 lujun9972 141 5 month  14 16:31 logfile
 To view logfile The content of the :
Log of bash -c sleep 2;date 
Mon May 14 16:31:42 2018

2018 years  05 month  14 day   week 1 16:31:44 CST

Mon May 14 16:31:44 2018
----------------

It can be seen that:

Although logfile could not be generated at the beginning of 1 due to the non-existence of logdir, logsave finally managed to generate logfile after creating logdir and wrote the execution result of date command into it. logsave not only writes the output of the command to logfile, but also includes the command executed, the start time of command execution, and the end time of command execution.

cmd_prog in logsave can be a special -, which means that logsave gets the content to be logged from standard input, making logsave available for use like tee 1

ls |wc -l |logsave /tmp/1.txt - >/dev/null
cat /tmp/1.txt

conclusion