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What does `LOGFILE=$1:-/var/log/syslog` do?
How to use syslog for else output ( show up with whois - query )?What does set -e do?What does this “printf” command do?“file /var/log/syslog is being edited” message in nanoscript does not write to file when executed from cronCron job log reads 'No MTA installed', does that prevent the CRON job from finishing?Direct all output to logfileWhat does “$@” do in a bash script?What does “exec 1>/var/opt/log/my_logs/MYPROG_`date '+%Y%m%d_%H%M%S'`.log 2>&1” do?Resume script does nothing
.everyoneloves__top-leaderboard:empty,.everyoneloves__mid-leaderboard:empty,.everyoneloves__bot-mid-leaderboard:empty margin-bottom:0;
6
I stumbled across this script containing:
LOGFILE=$1:-/var/log/syslog
What does this line do?
command-line bash
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
add a comment |
6
I stumbled across this script containing:
LOGFILE=$1:-/var/log/syslog
What does this line do?
command-line bash
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
Close enough IMO, heemayl’s answer explains thoroughly what the pattern with and without:does. If you don’t think the explanation suffices, maybe edit the answer over there? With 13 UVs on the question and 19 on the answer I think it’s save to say that this is our generic post for this particular parameter expansion, and we don’t really need to split things up even more – one post covering parameter expansion in general would be nice.
– dessert
9 hours ago
add a comment |
6
6
6
I stumbled across this script containing:
LOGFILE=$1:-/var/log/syslog
What does this line do?
command-line bash
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
I stumbled across this script containing:
LOGFILE=$1:-/var/log/syslog
What does this line do?
command-line bash
command-line bash
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
asked 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
50.6k12100195
Close enough IMO, heemayl’s answer explains thoroughly what the pattern with and without:does. If you don’t think the explanation suffices, maybe edit the answer over there? With 13 UVs on the question and 19 on the answer I think it’s save to say that this is our generic post for this particular parameter expansion, and we don’t really need to split things up even more – one post covering parameter expansion in general would be nice.
– dessert
9 hours ago
add a comment |
Close enough IMO, heemayl’s answer explains thoroughly what the pattern with and without:does. If you don’t think the explanation suffices, maybe edit the answer over there? With 13 UVs on the question and 19 on the answer I think it’s save to say that this is our generic post for this particular parameter expansion, and we don’t really need to split things up even more – one post covering parameter expansion in general would be nice.
– dessert
9 hours ago
Close enough IMO, heemayl’s answer explains thoroughly what the pattern with and without
: does. If you don’t think the explanation suffices, maybe edit the answer over there? With 13 UVs on the question and 19 on the answer I think it’s save to say that this is our generic post for this particular parameter expansion, and we don’t really need to split things up even more – one post covering parameter expansion in general would be nice.– dessert
9 hours ago
Close enough IMO, heemayl’s answer explains thoroughly what the pattern with and without
: does. If you don’t think the explanation suffices, maybe edit the answer over there? With 13 UVs on the question and 19 on the answer I think it’s save to say that this is our generic post for this particular parameter expansion, and we don’t really need to split things up even more – one post covering parameter expansion in general would be nice.– dessert
9 hours ago
add a comment |
1 Answer
1
active
oldest
votes
6
The command: LOGFILE=$1:-/var/log/syslog is shorthand for:
if [[ "$1" == "" ]] # if parameter 1 is blank
then
LOGFILE="/var/log/syslog" # LOGFILE set to /var/log/syslog
else
LOGFILE="$1" # LOGFILE set to parameter 1
fi
If parameter 1 is not passed you see:
If you pass paraemeter 1:
journalctl -b > /tmp/messages
yad-logfile /tmp/messages
you see:
The original code in question link was modified:
#!/bin/bash
# NAME: yad-logfile
# DATE: May 19, 2019.
# From: https://sourceforge.net/p/yad-dialog/wiki/LogViewer/
# This script demonstrates new features of list dialog. Script displays content
# of specified log file and mark some special strings: with word "kernel" by
# setting italic font, with word "error" by light yellow background and with
# word "warn" by pink background
LOGFILE=$1:-/var/log/syslog
PARSER='font=""; color="#FFFFFF";
/CRON/ font="italic";
/smartd/ color="#FFF4B8";
/upower/ color="#FFD0D8";
OFS="n" print $1 " " $2, $3, $4, substr($5,0,index($5,":")-1),
substr($0,index($0,$6)), font, color; fflush()'
cat $LOGFILE | awk "$PARSER" |
yad --title="Log viewer" --window-icon=logviewer
--button=gtk-close --geometry 600x350
--list --text="Content of $LOGFILE"
--column Date --column Time --column Host
--column Tag --column Message:TIP
--column @font@ --column @back@
exit $?
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
add a comment |
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6
The command: LOGFILE=$1:-/var/log/syslog is shorthand for:
if [[ "$1" == "" ]] # if parameter 1 is blank
then
LOGFILE="/var/log/syslog" # LOGFILE set to /var/log/syslog
else
LOGFILE="$1" # LOGFILE set to parameter 1
fi
If parameter 1 is not passed you see:
If you pass paraemeter 1:
journalctl -b > /tmp/messages
yad-logfile /tmp/messages
you see:
The original code in question link was modified:
#!/bin/bash
# NAME: yad-logfile
# DATE: May 19, 2019.
# From: https://sourceforge.net/p/yad-dialog/wiki/LogViewer/
# This script demonstrates new features of list dialog. Script displays content
# of specified log file and mark some special strings: with word "kernel" by
# setting italic font, with word "error" by light yellow background and with
# word "warn" by pink background
LOGFILE=$1:-/var/log/syslog
PARSER='font=""; color="#FFFFFF";
/CRON/ font="italic";
/smartd/ color="#FFF4B8";
/upower/ color="#FFD0D8";
OFS="n" print $1 " " $2, $3, $4, substr($5,0,index($5,":")-1),
substr($0,index($0,$6)), font, color; fflush()'
cat $LOGFILE | awk "$PARSER" |
yad --title="Log viewer" --window-icon=logviewer
--button=gtk-close --geometry 600x350
--list --text="Content of $LOGFILE"
--column Date --column Time --column Host
--column Tag --column Message:TIP
--column @font@ --column @back@
exit $?
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
add a comment |
6
The command: LOGFILE=$1:-/var/log/syslog is shorthand for:
if [[ "$1" == "" ]] # if parameter 1 is blank
then
LOGFILE="/var/log/syslog" # LOGFILE set to /var/log/syslog
else
LOGFILE="$1" # LOGFILE set to parameter 1
fi
If parameter 1 is not passed you see:
If you pass paraemeter 1:
journalctl -b > /tmp/messages
yad-logfile /tmp/messages
you see:
The original code in question link was modified:
#!/bin/bash
# NAME: yad-logfile
# DATE: May 19, 2019.
# From: https://sourceforge.net/p/yad-dialog/wiki/LogViewer/
# This script demonstrates new features of list dialog. Script displays content
# of specified log file and mark some special strings: with word "kernel" by
# setting italic font, with word "error" by light yellow background and with
# word "warn" by pink background
LOGFILE=$1:-/var/log/syslog
PARSER='font=""; color="#FFFFFF";
/CRON/ font="italic";
/smartd/ color="#FFF4B8";
/upower/ color="#FFD0D8";
OFS="n" print $1 " " $2, $3, $4, substr($5,0,index($5,":")-1),
substr($0,index($0,$6)), font, color; fflush()'
cat $LOGFILE | awk "$PARSER" |
yad --title="Log viewer" --window-icon=logviewer
--button=gtk-close --geometry 600x350
--list --text="Content of $LOGFILE"
--column Date --column Time --column Host
--column Tag --column Message:TIP
--column @font@ --column @back@
exit $?
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
add a comment |
6
6
6
The command: LOGFILE=$1:-/var/log/syslog is shorthand for:
if [[ "$1" == "" ]] # if parameter 1 is blank
then
LOGFILE="/var/log/syslog" # LOGFILE set to /var/log/syslog
else
LOGFILE="$1" # LOGFILE set to parameter 1
fi
If parameter 1 is not passed you see:
If you pass paraemeter 1:
journalctl -b > /tmp/messages
yad-logfile /tmp/messages
you see:
The original code in question link was modified:
#!/bin/bash
# NAME: yad-logfile
# DATE: May 19, 2019.
# From: https://sourceforge.net/p/yad-dialog/wiki/LogViewer/
# This script demonstrates new features of list dialog. Script displays content
# of specified log file and mark some special strings: with word "kernel" by
# setting italic font, with word "error" by light yellow background and with
# word "warn" by pink background
LOGFILE=$1:-/var/log/syslog
PARSER='font=""; color="#FFFFFF";
/CRON/ font="italic";
/smartd/ color="#FFF4B8";
/upower/ color="#FFD0D8";
OFS="n" print $1 " " $2, $3, $4, substr($5,0,index($5,":")-1),
substr($0,index($0,$6)), font, color; fflush()'
cat $LOGFILE | awk "$PARSER" |
yad --title="Log viewer" --window-icon=logviewer
--button=gtk-close --geometry 600x350
--list --text="Content of $LOGFILE"
--column Date --column Time --column Host
--column Tag --column Message:TIP
--column @font@ --column @back@
exit $?
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
The command: LOGFILE=$1:-/var/log/syslog is shorthand for:
if [[ "$1" == "" ]] # if parameter 1 is blank
then
LOGFILE="/var/log/syslog" # LOGFILE set to /var/log/syslog
else
LOGFILE="$1" # LOGFILE set to parameter 1
fi
If parameter 1 is not passed you see:
If you pass paraemeter 1:
journalctl -b > /tmp/messages
yad-logfile /tmp/messages
you see:
The original code in question link was modified:
#!/bin/bash
# NAME: yad-logfile
# DATE: May 19, 2019.
# From: https://sourceforge.net/p/yad-dialog/wiki/LogViewer/
# This script demonstrates new features of list dialog. Script displays content
# of specified log file and mark some special strings: with word "kernel" by
# setting italic font, with word "error" by light yellow background and with
# word "warn" by pink background
LOGFILE=$1:-/var/log/syslog
PARSER='font=""; color="#FFFFFF";
/CRON/ font="italic";
/smartd/ color="#FFF4B8";
/upower/ color="#FFD0D8";
OFS="n" print $1 " " $2, $3, $4, substr($5,0,index($5,":")-1),
substr($0,index($0,$6)), font, color; fflush()'
cat $LOGFILE | awk "$PARSER" |
yad --title="Log viewer" --window-icon=logviewer
--button=gtk-close --geometry 600x350
--list --text="Content of $LOGFILE"
--column Date --column Time --column Host
--column Tag --column Message:TIP
--column @font@ --column @back@
exit $?
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
answered 10 hours ago
WinEunuuchs2UnixWinEunuuchs2Unix
50.6k12100195
50.6k12100195
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
add a comment |
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
IMHO if [[ "$1" == "" ]] is not entirely equivalent. This tries to expand $1, whereas parameter expansion is intended for cases where $1 was not defined or unset. It is far more useful with environment variables like HOME for cases when they may be missing. Setting a variable to empty string in this code would produce similar effect but is not the same no variable in environment.
– Sergiy Kolodyazhnyy
2 hours ago
add a comment |
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Close enough IMO, heemayl’s answer explains thoroughly what the pattern with and without
:does. If you don’t think the explanation suffices, maybe edit the answer over there? With 13 UVs on the question and 19 on the answer I think it’s save to say that this is our generic post for this particular parameter expansion, and we don’t really need to split things up even more – one post covering parameter expansion in general would be nice.– dessert
9 hours ago