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Basic logging commands for Linux shell scripts
#!/bin/bash
##
## Simple logging mechanism for Bash
##
## Author: Michael Wayne Goodman <goodman.m.w@gmail.com>
## Thanks: Jul for the idea to add a datestring. See:
## http://www.goodmami.org/2011/07/simple-logging-in-bash-scripts/#comment-5854
## Thanks: @gffhcks for noting that inf() and debug() should be swapped,
## and that critical() used $2 instead of $1
##
## License: Public domain; do as you wish
##
exec 3>&2 # logging stream (file descriptor 3) defaults to STDERR
verbosity=3 # default to show warnings
silent_lvl=0
crt_lvl=1
err_lvl=2
wrn_lvl=3
inf_lvl=4
dbg_lvl=5
notify() { log $silent_lvl "NOTE: $1"; } # Always prints
critical() { log $crt_lvl "CRITICAL: $1"; }
error() { log $err_lvl "ERROR: $1"; }
warn() { log $wrn_lvl "WARNING: $1"; }
inf() { log $inf_lvl "INFO: $1"; } # "info" is already a command
debug() { log $dbg_lvl "DEBUG: $1"; }
log() {
if [ $verbosity -ge $1 ]; then
datestring=`date +'%Y-%m-%d %H:%M:%S'`
# Expand escaped characters, wrap at 70 chars, indent wrapped lines
echo -e "$datestring $2" | fold -w70 -s | sed '2~1s/^/ /' >&3
fi
}
@gffhcks
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gffhcks commented Sep 21, 2015

Shouldn't "debug" be at a higher level of verbosity than "info"?

Also, why does $2 get used instead of $1 for critical()?

@goodmami
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@gffhcks, sorry to be so late to respond. I didn't get any notification for your comment.

And thanks for pointing these out. Debug and Info are in the unconventional order because I didn't closely check with what other logging frameworks do. I'm not sure why I used $2 in critical(); that's just a bug. I'll fix both of these.

@MapleLove2014
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Hello, what does this statement means: sed '2~1s/^/ /' ?

@goodmami
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@MapleLove2014, that indents the wrapped lines. 2~1 means to perform the following operation on every line starting from the 2nd (every 1 line after line 2), then s/^/ / is a substitution operation that matches the beginning of each line (^) and inserts two spaces. In a terminal you might try man sed to get more info about the command.

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