Logging tool for command-line terminal and batch

Introduction

This shell script log4t permits to log to files every text written to standard output and standard error streams by the execution of a batch or a command-line into a terminal, as well as text sent to the standard input stream.

log4t is written in kornshell (compatible with ksh and ksh93). Don't hesitate to port it to bash if you know about bash coprocesses (and let me know !).

For instance, you can log the result of the command ls README.md toto with:

> ./log4t ls README.md toto
(+0) [ls] L ----- START execution of 'ls README.md toto' (process 6437 submitted by laurent@amedea6:***)
(+0) [ls] L ----- Log file:   ls.20210612T210810.6437.log
(+0) [ls] L ----- Error file: ls.20210612T210810.6437.err
(+0) [ls] E ls: cannot access 'toto': No such file or directory
(+0) [ls] O README.md
(+0) [ls] L ----- FATAL ERROR (return code 2)
(+0) [ls] L ----- END execution of 'ls README.md toto' after 0.014 seconds (return code 2)
(+0) [ls] L ----- Log file:   ls.20210612T210810.6437.log
(+0) [ls] L ----- Error file: ls.20210612T210810.6437.err

Traces of execution are logged in a default log file. Errors are sent a separate log file.

> cat ls.20210612T210810.6437.log
2021-06-12T21:08:10 [ls] L ----- START execution of 'ls README.md toto' (process 6437 submitted by laurent@amedea6:***)
2021-06-12T21:08:10 [ls] L ----- Error file: ls.20210612T210810.6437.err
2021-06-12T21:08:10 [ls] O README.md
2021-06-12T21:08:10 [ls] L ----- FATAL ERROR (return code 2)
2021-06-12T21:08:10 [ls] E ls: cannot access 'toto': No such file or directory
2021-06-12T21:08:10 [ls] L ----- END execution of 'ls README.md toto' after 0.014 seconds (return code 2)
2021-06-12T21:08:10 [ls] L ----- Error file: ls.20210612T210810.6437.err

> cat ls.20210612T210810.6437.err
2021-06-12T21:08:10 [ls] L ----- START execution of 'ls README.md toto' (process 6437 submitted by laurent@amedea6:***)
2021-06-12T21:08:10 [ls] E ls: cannot access 'toto': No such file or directory
2021-06-12T21:08:10 [ls] L ----- FATAL ERROR (return code 2)
2021-06-12T21:08:10 [ls] L ----- END execution of 'ls README.md toto' after 0.014 seconds (return code 2)

Help page

Type log4t -h for options.

Name:

log4t - executes a command and duplicates its terminal outputs to log files

Usage:

log4t [-ahnrl] [{-|+}IOE] [-o filename] command [arguments...]

Description:

The log4t command makes time-stamped typescripts of everything read from standard input and displayed to standard output and standard error during the execution of command.

Typescripts are written to two log files, a standard log file (suffixed .log) and an error log file (suffixed .err).

The command command is executed. command must be executable.
The standard output (file descriptor 1) of "command" is:
- typescripted to the standard log file if the standard output is associated with a terminal device or option +O is used.
- typescripted to the standard output if it is associated to a terminal device. Otherwise, the standard output is kept unchanged.
The standard input (file descriptor 0) of command is:
- typescripted to the standard log file if the standard input is associated with a terminal device or option +I is used.
- typescripted to the standard error if the standard error is associated to a terminal device.
The standard error (file descriptor 2) of command is:
- typescripted to the standard log file and the error log file if the standard error is associated with a terminal device or option +E is used.
- typescripted to standard error if it is associated to a terminal device. Otherwise, the standard error is kept unchanged.
The return status of the invoked command is returned.
The SIGHUP signals are ignored during execution of command, allowing the user to logout before the execution ends (same as nohup) when run in background.

Options:

-a Appends the typescripts to the log and error files.

-r Log and error files are overwritten.

-o filename If filename is an existing directory, specifies the directory where log files are written into. Otherwise, specifies the basename for log files.

-n No log and error files are created.

-h Displays this help message.

-l (lowercase ell) Typescript written with long format (process id and line numbering).

{-|+}I (uppercase i) Desactivate/activate logging for standard input. -I is needed if log4t is run as a background process (to avoid signal TTIN).

{-|+}O Desactivate/activate logging for standard output.

{-|+}E Desactivate/activate logging for standard error.

Names of log files:

Log files are written into the current directory, except if options -o is used and specifies an existing directory.
New output log files are created, except if options -a, -r or -n are used.
The basename of log files can be specified with option -o filename. By default, command is used as basename.
If options -a or -r are used, filenames are basename.log and basename.err for standard and error log files respectively.
Otherwise, filenames are basename.date.pid.log and basename.date.pid.err for standard and error log files respectively.

Typescripting format:

to terminal : (+S) [L] T message
to log file (short format) : D [L] T message
to log file (long format, option -l) : D (+ss) P [L] T:N message where:
- S is the number of elapsed seconds since the beginning of the execution of command
- L is the basename of log files
- T is the type of standard stream typescripted (I for input, O for output, E for error)
- D is the current date with format year-month-day hour:minute:second
- P is the process id of the process log4t
- N is the line number (one separate numbering for each standard stream)

Return status:

If command is invoked, the exit status of log4t will be the exit status of command.
Otherwise, log4t will exit with one of the following values:
- 1-125 an error occurred in log4t.
- 126 command was found but could not be invoked.
- 127 command is unspecified, empty or could not be found.

Examples:

log4t ls invokes the executable /bin/ls standard and error output written to files named (for example) ls.20210612211653.6518.log and ls.20210612211653.6518.err.

log4t +O -l script.ksh >/dev/null invokes the executable script script.ksh, standard output is not sent to the terminal (> /dev/null) but is logged anyway (+O) with a long format (-l).

log4t -n ksh -c "pwd ; ls -1 | wc -l" : the command /usr/bin/ksh is invoked and executed without creating a log file (-n).

log4t -r -o output ksh -c 'sleep 1 ; print 1 ; sleep 1 ; print -u2 2 ; sleep 1 ; return 7' ; print $? : log4t return code is the return code (7) of the command launched, ksh in this example.

log4t -Io test ksh -c 'i=0 ; while (( i=i+1 )) ; do sleep 10 ; print $i ; done' & : the user can logout without killing the process launched in the background (&) (note the needed option -I used since).

log4t $SHELL makes a time-stamped record of a terminal session.

log4t -ro mylog +O cat log4t | wc -c ; cat log4t | wc -c : the command "cat log4t" is executed and its standard output is logged (+O) to file mylog.log (-ro wc) while piped unmodified to command wc -l.

log4t can also be used to log scheduled tasks, such as with cron, adding the following to the crontab: 28 14 * * * logit +OE ls /home/laurent aaaaa >/dev/null

the command ls /home/laurent aaaaa >/dev/null is executed and logged. Errors are reported by the system ans logged in the error log file.

farhiongit/log4t