I wrote a shell script to gather and show some information after a successful login.
However some info is taking some time to gather so I print to the terminal (ssh putty) ahead some headers and already available info before go back and print the delayed info into the right place.
To accomplish that I used the following script to get the current cursor position, (ignoring all the boring stuff that come before. It's a bunch of printf's, cat and cut's...
. ...
. ...
printf "^[[0m""\n"
# Get current settings.
if ! termios="$(stty -g 2>/dev/null)" ; then
echo "Not running in a terminal." >&2
exit 1
fi
# Restore terminal settings when the script exits.
trap "stty '$termios'" EXIT
# Disable ICANON ECHO. Should probably also disable CREAD.
stty -icanon -echo
# Request cursor coordinates
printf '\033[6n'
# Read response from standard input; note, it ends at R, not at newline
read -d "R" rowscols
# Clean up the rowscols (from \033[rows;cols -- the R at end was eaten)
rowscols="${rowscols//[^0-9;]/}"
rowscols=("${rowscols//;/ }")
#printf '(row %d, column %d)\n' ${rowscols[0]} ${rowscols[1]} *<-- commented by me*
# Reset original terminal settings.
stty "$termios"
# To the stuff...
printf '(row %d, column %d)\n' ${rowscols[0]} ${rowscols[1]}
line=${rowscols[0]}
line=$(($line - 10)) *<--- Indeed script's line 102. I want subtract 10*
col=56
printf '(r= %d, c= %d)\n' ${line} ${col} *<--- Printed two times, both times wrong values*
exit 1 *<--- Put here just to exit earlier*
## Get uptime/activetime formated to my taste.
m_activetime=$(/usr/bin/activetime -v)
printf "\33[%d;%dH^[[38;5;196m ${m_activetime}" ${line} ${col}
. ...
. ...
When I run the code i get:
. ...
. ...
. ...
||=-= _ |-=- |+++++++| _ ||= _ | :
`~‾‾ '--~~__|- = |+++++__|----~‾ ‾~`---', CPU stat⸱:
~---__|,--~' Weather⸱⸱:
(row 16, column 1)
./c.asc: line 102: 16 1 - 10: syntax error in expression (error token is "1 - 10")
(r= 16, c= 1)
(r= 56, c= 0)
lr#pi:~ $
1) Script is bash (shebang #!/usr/bash)
2) The line (row 16, column 1) seems OK!
3) The script is called c.asc
4) I wonder what the heck that error is, I've used similar expressions before, not with bash arrays but even so...
line 102: 16 1 - 10: syntax error
I can guess the 16, but where did it come the 1 - 10 ?
(error token is "1 - 10")
what token "1 - 10" ????!!!
5) The first (r= 16, c= 1) is already wrong, it should be (r= 6, c= 56). Why is this? What happened to the subtraction of 10? Where did it go the value of the variable col?
6) Even more strange. I didn't instruct to print a second time, even so, now the variable line has an identity crisis and display the col value, and in both cases the instruction col=56 seems to have been ignored. Why and how did the variable line get the value of the variable col? Why did the variable col shift from the wrong value 1, to the wrong value 0?
7) The showed script has been transformed to track the error. It started by not printing into the expected position, and display errors. Also a version of the the printf printf '(r= %d, c= %d)\n' $((${line} - 10)) ${col} display equally similar and bizarre error.
p.s.
After some additional experiments with only the part of the script to get the terminal cursor position, it seems also that it is not completely sane. It returns the position alright but trying things like read r c < <(curspos), (assuming that curspos is the name of the script that return the tuple lin col), the prompt hangs until Ctrl-C is pressed and after that prompt goes crazy.
Thank you
The issue is that you're quoting the value to the array.
rowscols=("${rowscols//;/ }")
This tells bash to ignore the spaces and consider it as one value. So when you get the first value with ${rowscols[0]} later, you actually get 16 1 instead of 16 and there's no second value.
It also worked with this printf because you didn't quote the values there.
printf '(row %d, column %d)\n' ${rowscols[0]} ${rowscols[1]}
I don't know why it ran the last printf twice, but it seems to be solved with the quoting.
Related
When I am executing the below script, I am getting the following error :-
The script executes infintely and below line is printed everytime.
"line 9: 1=1+2: command not found". Why?
#!/bin/bash
echo "Script 1 - Linux Scripting Book"
x=1
while [ $x -le 45 ]
do
echo x : $x
$x=$x+2
done
echo "End Of Script 1"
exit 0
Also if I change the $x=$x+2 to x+$x+2 then also I am getting the below error.
line 6: [: 1+2: integer expression expected
Same script when executed like this runs fine.
#!/bin/bash
echo "Script 1 - Linux Scripting Book"
x=1
while [ $x -le 45 ]
do
echo x : $x
let x=x+2
done
echo "End Of Script 1"
exit 0
You get line 9: 1=1+2: command not found because 1=1+2 is what $x=$x+2 is expanded into.
Use expr or let or ((...)) for integer calculations and bc for floating point:
let x=x+2
((x=x+2)) #same as above
((x+=2)) #same
((x++)) #if adding just one
((++x)) #if adding just one
x=$((x+2))
x=`expr $x + 2` #space before and after +
x=$(echo $x+2|bc) #using bc
x=$(echo $x+2.1|bc) #bc also works with floating points (numbers with decimals)
Since this part of the question isn't cleared yet, and not fine to post in a comment, I add this partial answer:
x=1; for i in 1 2 3 ; do x=$x+2; echo $x; done
1+2
1+2+2
1+2+2+2
As a side note: Don't use exit 0 at the end of your script without a good reason. When the script is done, it exits by itself without your help. The exit status will be the exit status of the last command performed, in your case a simple echo, which will almost always succeed. In the rare cases it fails, you will probably without intention hide that failure.
If you source the script, the exit will throw you out of your running shell.
But you can rewrite your while loop like this:
x=0
while (($((x)) < 9))
do
echo x : $x
x=$x+2
done
echo $((x))
x : 0
x : 0+2
x : 0+2+2
x : 0+2+2+2
x : 0+2+2+2+2
10
Because that's not the Bourne shell syntax for setting a variable; it looks more like Perl or PHP. The $ is used for parameter expansion and is not part of the variable name. Variable assignment simply uses =, and let evaluates arithmetic expressions (much like $((expression))). Another syntax that should work is x=$((x+2)). Note that these arithmetic evaluations are a bash feature; standard unix shells might require use of external tools such as expr.
Case scenario:
$ cat Status.txt
1,connected
2,connected
3,connected
4,connected
5,connected
6,connected
7,disconnected
8,disconnected
9,disconnected
10,disconnected
11,disconnected
12,disconnected
13,disconnected
14,connected
15,connected
16,connected
17,disconnected
18,connected
19,connected
20,connected
21,disconnected
22,disconnected
23,disconnected
24,disconnected
25,disconnected
26,disconnected
27,disconnected
28,disconnected
29,disconnected
30,connected
As can be seen, there are "hollows", understanding them as lines with the "disconnected" value inside the sequence file.
I want, in fact, to detect these "holes", but it would be useful if I could set a minimum n of missing numbers in the sequence.
I.e: for ' n=5' a detectable hole would be the 7... 13 part, as there are at least 5 "disconnected" in a row on the sequence. However, the missing 17 should not be considered as detectable in this case. Again, at line 21 whe get a valid disconnection.
Something like:
$ detector Status.txt -n 5 --pattern connected
7
21
... that could be interpreted like:
- Missing more than 5 "connected" starting at 7.
- Missing more than 5 "connected" starting at 21.
I need to script this on Linux shell, so I was thinking about programing some loop, parsing strings and so on, but I feel like if this could be done by using linux shell tools and maybe some simpler programming. Is there a way?
Even when small programs like csvtool are a valid solution, some more common Linux commands (like grep, cut, awk, sed, wc... etc) could be worth for me when working with embedded devices.
#!/usr/bin/env bash
last_connected=0
min_hole_size=${1:-5} # default to 5, or take an argument from the command line
while IFS=, read -r num state; do
if [[ $state = connected ]]; then
if (( (num-last_connected) > (min_hole_size+1) )); then
echo "Found a hole running from $((last_connected + 1)) to $((num - 1))"
fi
last_connected=$num
fi
done
# Special case: Need to also handle a hole that's still open at EOF.
if [[ $state != connected ]] && (( num - last_connected > min_hole_size )); then
echo "Found a hole running from $((last_connected + 1)) to $num"
fi
...emits, given your file on stdin (./detect-holes <in.txt):
Found a hole running from 7 to 13
Found a hole running from 21 to 29
See:
BashFAQ #1 - How can I read a file (data stream, variable) line-by-line (and/or field-by-field)?
The conditional expression -- the [[ ]] syntax used to make it safe to do string comparisons without quoting expansions.
Arithmetic comparison syntax -- valid in $(( )) in all POSIX-compliant shells; also available without the expansion side effects as (( )) as a bash extension.
This is the perfect use case for awk, since the machinery of line reading, column splitting, and matching is all built in. The only tricky bit is getting the command line argument to your script, but it's not too bad:
#!/usr/bin/env bash
awk -v window="$1" -F, '
BEGIN { if (window=="") {window = 1} }
$2=="disconnected"{if (consecutive==0){start=NR}; consecutive++}
$2!="disconnected"{if (consecutive>window){print start}; consecutive=0}
END {if (consecutive>window){print start}}'
The window value is supplied as the first command line argument; left out, it defaults to 1, which means "display the start of gaps with at least two consecutive disconnections". Probably could have a better name. You can give it 0 to include single disconnections. Sample output below. (Note that I added series of 2 disconnections at the end to test the failure that Charles metions).
njv#organon:~/tmp$ ./tst.sh 0 < status.txt # any number of disconnections
7
17
21
31
njv#organon:~/tmp$ ./tst.sh < status.txt # at least 2 disconnections
7
21
31
njv#organon:~/tmp$ ./tst.sh 8 < status.txt # at least 9 disconnections
21
Awk solution:
detector.awk script:
#!/bin/awk -f
BEGIN { FS="," }
$2 == "disconnected"{
if (f && NR-c==nr) c++;
else { f=1; c++; nr=NR }
}
$2 == "connected"{
if (f) {
if (c > n) {
printf "- Missing more than 5 \042connected\042 starting at %d.\n", nr
}
f=c=0
}
}
Usage:
awk -f detector.awk -v n=5 status.txt
The output:
- Missing more than 5 "connected" starting at 7.
- Missing more than 5 "connected" starting at 21.
I'm trying to batch modify some images using a bash script, and to print out the progress. It looks to me like bash is interpreting the increment to counter as a command and is giving the following error:
augment_data.sh: line 20: 0: command not found
Here is the code:
for file in *.jpg
do
convert $file -rotate 90 rotated_"$file"
((counter++))
if $((counter % 10 == 0)); then
echo "Rotated $counter files out of $num_files"
fi
done
with line 20 being the one with the counter increment operation.
How can I fix this so that I don't get the error message?
In an arithmetic substitution, the result of an arithmetic operation is substituted in the position of the operation itself.
In this case, $(( 1 == 0 )) has an arithmetic result of 0, and $(( 1 == 1 )) has a result of 1.
Thus, if you use $(( ... )), then this 0 or 1 is substituted in that position, and so gets run as a command. Since you don't have commands named 0 or 1 (probably), either of these will result in a command not found error.
If you use (( ... )), then the arithmetic result directly sets return value, but no expansion takes place.
I've been trying to customize my Bash prompt so that it will look like
[feralin#localhost ~]$ _
with colors. I managed to get constant colors (the same colors every time I see the prompt), but I want the username ('feralin') to appear red, instead of green, if the last command had a nonzero exit status. I came up with:
\e[1;33m[$(if [[ $? == 0 ]]; then echo "\e[0;31m"; else echo "\e[0;32m"; fi)\u\e[m#\e[1;34m\h \e[0;35m\W\e[1;33m]$ \e[m
However, from my observations, the $(if ...; fi) seems to be evaluated once, when the .bashrc is run, and the result is substituted forever after. This makes the name always green, even if the last exit code is nonzero (as in, echo $?). Is this what is happening? Or is it simply something else wrong with my prompt? Long question short, how do I get my prompt to use the last exit code?
As you are starting to border on a complex PS1, you might consider using PROMPT_COMMAND. With this, you set it to a function, and it will be run after each command to generate the prompt.
You could try the following in your ~/.bashrc file:
PROMPT_COMMAND=__prompt_command # Function to generate PS1 after CMDs
__prompt_command() {
local EXIT="$?" # This needs to be first
PS1=""
local RCol='\[\e[0m\]'
local Red='\[\e[0;31m\]'
local Gre='\[\e[0;32m\]'
local BYel='\[\e[1;33m\]'
local BBlu='\[\e[1;34m\]'
local Pur='\[\e[0;35m\]'
if [ $EXIT != 0 ]; then
PS1+="${Red}\u${RCol}" # Add red if exit code non 0
else
PS1+="${Gre}\u${RCol}"
fi
PS1+="${RCol}#${BBlu}\h ${Pur}\W${BYel}$ ${RCol}"
}
This should do what it sounds like you want. Take a look a my bashrc's sub file if you want to see all the things I do with my __prompt_command function.
If you don't want to use the prompt command there are two things you need to take into account:
getting the value of $? before anything else. Otherwise it'll be overridden.
escaping all the $'s in the PS1 (so it's not evaluated when you assign it)
Working example using a variable
PS1="\$(VALU="\$?" ; echo \$VALU ; date ; if [ \$VALU == 0 ]; then echo zero; else echo nonzero; fi) "
Working example without a variable
Here the if needs to be the first thing, before any command that would override the $?.
PS1="\$(if [ \$? == 0 ]; then echo zero; else echo nonzero; fi) "
Notice how the \$() is escaped so it's not executed right away, but each time PS1 is used. Also all the uses of \$?.
Compact solution:
PS1='... $(code=${?##0};echo ${code:+[error: ${code}]})'
This approach does not require PROMPT_COMMAND (apparently this can be slower sometimes) and prints [error: <code>] if the exit code is non-zero, and nothing if it's zero:
... > false
... [error: 1]> true
... >
Change the [error: ${code}] part depending on your liking, with ${code} being the non-zero code to print.
Note the use of ' to ensure the inline $() shell gets executed when PS1 is evaluated later, not when the shell is started.
As bonus, you can make it colorful in red by adding \e[01;31m in front and \e[00m after to reset:
PS1='... \e[01;31m$(code=${?##0};echo ${code:+[error: ${code}]})\e[00m'
--
How it works:
it uses bash parameter substitution
first, the ${?##0} will read the exit code $? of the previous command
the ## will remove any 0 pattern from the beginning, effectively making a 0 result an empty var (thanks #blaskovicz for the trick)
we assign this to a temporary code variable as we need to do another substitution, and they can't be nested
the ${code:+REPLACEMENT} will print the REPLACEMENT part only if the variable code is set (non-empty)
this way we can add some text and brackets around it, and reference the variable again inline: [error: ${code}]
I wanted to keep default Debian colors, print the exact code, and only print it on failure:
# Show exit status on failure.
PROMPT_COMMAND=__prompt_command
__prompt_command() {
local curr_exit="$?"
local BRed='\[\e[0;91m\]'
local RCol='\[\e[0m\]'
PS1='${debian_chroot:+($debian_chroot)}\[\033[01;32m\]\u#\h\[\033[00m\]:\[\033[01;34m\]\w\[\033[00m\]\$ '
if [ "$curr_exit" != 0 ]; then
PS1="[${BRed}$curr_exit${RCol}]$PS1"
fi
}
The following provides a leading green check mark when the exit code is zero and a red cross in all other cases. The remainder is a standard colorized prompt. The printf statements can be modified to present the two states that were originally requested.
PS1='$(if [ $? -eq 0 ]; then printf "\033[01;32m""\xE2\x9C\x93"; else printf "\033[01;31m""\xE2\x9C\x95"; fi) \[\e[00;32m\]\u#\h\[\e[00;30m\]:\[\e[01;33m\]\w\[\e[01;37m\]\$ '
Why didn't I think about that myself? I found this very interesting and added this feature to my 'info-bar' project. Eyes will turn red if the last command failed.
#!/bin/bash
eyes=(O o ∘ ◦ ⍤ ⍥) en=${#eyes[#]} mouth='_'
face () { # gen random face
[[ $error -gt 0 ]] && ecolor=$RED || ecolor=$YLW
if [[ $1 ]]; then printf "${eyes[$[RANDOM%en]]}$mouth${eyes[$[RANDOM%en]]}"
else printf "$ecolor${eyes[$[RANDOM%en]]}$YLW$mouth$ecolor${eyes[$[RANDOM%en]]}$DEF"
fi
}
info () { error=$?
[[ -d .git ]] && { # If in git project folder add git status to info bar output
git_clr=('GIT' $(git -c color.ui=always status -sb)) # Colored output 4 info
git_tst=('GIT' $(git status -sb)) # Simple output 4 test
}
printf -v line "%${COLUMNS}s" # Set border length
date=$(printf "%(%a %d %b %T)T") # Date & time 4 test
test=" O_o $PWD ${git_tst[*]} $date o_O " # Test string
step=$[$COLUMNS-${#test}]; [[ $step -lt 0 ]] && step=0 # Count spaces
line="$GRN${line// /-}$DEF\n" # Create lines
home="$BLD$BLU$PWD$DEF" # Home dir info
date="$DIM$date$DEF" # Colored date & time
#------+-----+-------+--------+-------------+-----+-------+--------+
# Line | O_o |homedir| Spaces | Git status | Date| o_O | Line |
#------+-----+-------+--------+-------------+-----+-------+--------+
printf "$line $(face) $home %${step}s ${git_clr[*]} $date $(face) \n$line" # Final info string
}
PS1='${debian_chroot:+($debian_chroot)}\n$(info)\n$ '
case "$TERM" in xterm*|rxvt*)
PS1="\[\e]0;${debian_chroot:+($debian_chroot)} $(face 1) \w\a\]$PS1";;
esac
Improved demure answer:
I think this is important because the exit status is not always 0 or 1.
if [ $EXIT != 0 ]; then
PS1+="${Red}${EXIT}:\u${RCol}" # Add red if exit code != 0
else
PS1+="${Gre}${EXIT}:\u${RCol}" # Also displays exit status
fi
To preserve the original prompt format (not just colors),
you could append following to the end of file ~/.bashrc:
PS1_ORIG=$PS1 # original primary prompt value
PROMPT_COMMAND=__update_prompt # Function to be re-evaluated after each command is executed
__update_prompt() {
local PREVIOUS_EXIT_CODE="$?"
if [ $PREVIOUS_EXIT_CODE != 0 ]; then
local RedCol='\[\e[0;31m\]'
local ResetCol='\[\e[0m\]'
local replacement="${RedCol}\u${ResetCol}"
# Replace username color
PS1=${PS1_ORIG//]\\u/]$replacement}
## Alternative: keep same colors, append exit code
#PS1="$PS1_ORIG[${RedCol}error=$PREVIOUS_EXIT_CODE${ResetCol}]$ "
else
PS1=$PS1_ORIG
fi
}
See also the comment about the alternative approach that preserves username color and just appends an error code in red to the end of the original prompt format.
You can achieve a similar result to include a colored (non-zero) exit code in a prompt, without using subshells in the prompt nor prompt_command.
You color the exit code portion of the prompt, while having it only appear when non-zero.
Core 2$ section of the prompt: \\[\\033[0;31;4m\\]\${?#0}\\[\\033[0;33m\\]\$ \\[\\033[0m\\]
Key elements:
return code, if not 0: \${?#0} (specificly "removes prefix of 0")
change color without adding to calculated prompt-width: \\[\\033[0;31m\\]
\\[ - begin block
\\033 - treat as 0-width, in readline calculations for cmdline editing
[0;31;4m - escape code, change color, red fg, underline
\\] - end block
Components:
\\[\\033[0;31;4m\\] - set color 0;31m fg red, underline
\${?#0} - display non-zero status (by removing 0 prefix)
\\[\\033[0;33m\\] - set color 0;33m fg yellow
\$ - $ or # on EUID
\\[\\033[0m\\] - reset color
The full PS1 I use (on one host):
declare -x PS1="\\[\\033[0;35m\\]\\h\\[\\033[1;37m\\] \\[\\033[0;37m\\]\\w \\[\\033[0;33m\\]\\[\\033[0;31;4m\\]\${?#0}\\[\\033[0;33m\\]\$ \\[\\033[0m\\]"
Note: this addresses a natural extension to this question, in a more enduring way then a comment.
Bash
function my_prompt {
local retval=$?
local field1='\u#\h'
local field2='\w'
local field3='$([ $SHLVL -gt 1 ] && echo \ shlvl:$SHLVL)$([ \j -gt 0 ] && echo \ jobs:\j)'"$([ ${retval} -ne 0 ] && echo \ exit:$retval)"
local field4='\$'
PS1=$'\n'"\e[0;35m${field1}\e[m \e[0;34m${field2}\e[m\e[0;31m${field3}\e[m"$'\n'"\[\e[0;36m\]${field4}\[\e[m\] "
}
PROMPT_COMMAND="my_prompt; ${PROMPT_COMMAND}"
Zsh
PROMPT=$'\n''%F{magenta}%n#%m%f %F{blue}%~%f%F{red}%(2L. shlvl:%L.)%(1j. jobs:%j.)%(?.. exit:%?)%f'$'\n''%F{cyan}%(!.#.$)%f '
Images of prompt
I am using below script ,
clear
tput cup 1
echo "1";
tput cup 2
echo "2";
tput cup 4
echo "3";
then Out put is coming like
1
2
3
If i use wrong script like ,
clear
tput cup 1
echo "1";
tput cup 2
echo ;"2";
tput cup 3
echo "3";
then out put is
1
3/var.sh: line 5: 2: command not found
This means in third line 3 printed and 2 line error also printed .
So is there any way to detect error line number to print 3 after error?
EDIT:
when I use -x , output is
[root#srinivas Installation]# sh -x var.sh
+ clear
+ tput cup 1
+ echo 1
+ echo
+ echo 3up 2
3 2
[root#srinivas Installation]# found
+ tput cup 3
If you run your shell script with the -x option, it'll show you each line as it executes.
This is because standard output and standard error are printed in different ways - Standard output is synchronous, meaning the lines will be printed in sequence and as they arrive, while standard error is asynchronous, which means it's printed whenever the terminal can fit it in. One way to fix this is to chunk standard error together with standard output:
/var.sh 2>&1
More details in Greg's wiki.
PS: All the semicolons in the file are unnecessary - If your commands are separated by newlines, semicolons will never be necessary.
That output looks like what should be expected. Here's the sequence:
tput cup 1
echo "1"
Move to line 1 and output a 1. This works properly.
tput cup 2
echo ;"2";
Move to line 2, then output a blank line (echo with no arguments) which moves to line 3. Then execute a program named 2, which the script can't find, resulting in the error message ./var.sh: line 5: 2: command not found printed on line 3.
tput cup 3
echo "3";
Move to line 3 and output a 3, which overwrites the . in the above error message. Resulting in the final apparent output that you note, even though it wasn't produced in a strictly left-to-right top-to-bottom order.