I wanted to delete commands that are common (such as pwd, ls -l, cd, ) and keep the ones that I might forget how to use. To do this I ran the following commands
history | grep "cd$" | cut -c 1-5 > ~/sandboxArea/histDelTemp.txt
cntr=0; for i in $(cat ~/sandboxArea/histDelTemp.txt); do var=`expr $i - $cntr`; history -d $var; cntr=`expr $cntr + 1`; done; unset cntr
After running the above command if I again run to check if everything was deleted using the following command
history | grep "cd$"
then it seems that everything is in fact deleted and the above command produces no output.
However, if I close the terminal and again run the above command then everything seems to re-appear. Why is it so? Does bash has functionality to backup_restore commands?
Thanks in advance
Related
In Linux I use InfluxDB which can make a backup of the database for archival purposes. Each backup comprises a series of files with the same prefix "/tank/Backups/var/Influxdb/20191225T235655Z." and different extensions.
I wanted to write a bash script which first deletes the oldest existing backups, then creates a new one (here I paste only the removal):
ls -tp /tank/Backups/var/Influxdb/* | grep -v '/$' | sed -E 's/\..+//' | \
sort -ru | sed 's/$/.*/' | tail -n +4 | xargs -d '\n' -r rm --
However, when I run the script as "sudo", I get
rm: cannot remove '/tank/Backups/var/Influxdb/20191225T235655Z.*': No such file or directory
When I run the quoted script, except the latest part, I get:
/tank/Backups/var/Influxdb/20190930T215357Z.*
/tank/Backups/var/Influxdb/20190930T215352Z.*
which is correct. Also, if I manually write
sudo /tank/Backups/var/Influxdb/20190930T215357Z.*
the command succeeds.
Why is the script reporting an error?
I'm using Ubuntu 18.04 and the folder "/tank" is a ZFS volume.
Better do :
find /tank/Backups/var/Influxdb/* -mtime +5 -delete
to remove files older than 5 days.
Then, you can run the next command
Explaining the Error
This answer is only here to explain the error and give a deeper understanding of what is happening. If you are simply looking for an elegant solution search for other answers.
When I run the quoted script, except the latest part, I get:
/tank/Backups/var/Influxdb/20190930T215357Z.*
/tank/Backups/var/Influxdb/20190930T215352Z.*
which is correct
The listed strings are not what you want. When you pass these paths to rm it sees them just as literal strings, that is, two files whose names end with a literal *. Since you don't have such files you get an error.
When you type rm * manually into your console bash (not rm!) does globbing. bash searches files and replaces the * with the list of found files. Only after that bash executes rm foundFile1 foundFile2 .... rm never sees the *.
Strings inside a pipeline are not processed by bash, but by the commands in the pipeline, in your case rm. rm does not glob.
You could run bash inside your pipeline and let it expand the * you inserted earlier. To this end, replace the last command in your pipeline with xargs -r bash -c 'rm -- $*' --. However, note that your paths are not quoted here. If there are spaces or literal * in your filenames the command will break. This is necessary for globbing as quoted "*" are not expanded by bash.
To quote your files you have to insert the * glob inside the bash command:
ls -tp /tank/Backups/var/Influxdb/* | grep -v '/$' | sed -E 's/\..+//' |
sort -ru | tail -n +4 | xargs -d\\n -L1 -r bash -c 'rm -- "$0."*'
Above command is only a simple fix for your command. It is neither elegant nor very robust. Using tools like find is strongly recommended.
I have a shell script of more than 1000 lines, i would like to check if all the commands used in the script are installed in my Linux operating system.
Is there any tool to get the list of Linux commands used in the shell script?
Or how can i write a small script which can do this for me?
The script runs successfully on the Ubuntu machine, it is invoked as a part of C++ application. we need to run the same on a device where a Linux with limited capability runs. I have identified manually, few commands which the script runs and not present on Device OS. before we try installing these commands i would like to check all other commands and install all at once.
Thanks in advance
I already tried this in the past and got to the conclusion that is very difficult to provide a solution which would work for all scripts. The reason is that each script with complex commands has a different approach in using the shells features.
In case of a simple linear script, it might be as easy as using debug mode.
For example: bash -x script.sh 2>&1 | grep ^+ | awk '{print $2}' | sort -u
In case the script has some decisions, then you might use the same approach an consider that for the "else" cases the commands would still be the same just with different arguments or would be something trivial (echo + exit).
In case of a complex script, I attempted to write a script that would just look for commands in the same place I would do it myself. The challenge is to create expressions that would help identify all used possibilities, I would say this is doable for about 80-90% of the script and the output should only be used as reference since it will contain invalid data (~20%).
Here is an example script that would parse itself using a very simple approach (separate commands on different lines, 1st word will be the command):
# 1. Eliminate all quoted text
# 2. Eliminate all comments
# 3. Replace all delimiters between commands with new lines ( ; | && || )
# 4. extract the command from 1st column and print it once
cat $0 \
| sed -e 's/\"/./g' -e "s/'[^']*'//g" -e 's/"[^"]*"//g' \
| sed -e "s/^[[:space:]]*#.*$//" -e "s/\([^\\]\)#[^\"']*$/\1/" \
| sed -e "s/&&/;/g" -e "s/||/;/g" | tr ";|" "\n\n" \
| awk '{print $1}' | sort -u
the output is:
.
/
/g.
awk
cat
sed
sort
tr
There are many more cases to consider (command substitutions, aliases etc.), 1, 2 and 3 are just beginning, but they would still cover 80% of most complex scripts.
The regular expressions used would need to be adjusted or extended to increase precision and special cases.
In conclusion if you really need something like this, then you can write a script as above, but don't trust the output until you verify it yourself.
Add export PATH='' to the second line of your script.
Execute your_script.sh 2>&1 > /dev/null | grep 'No such file or directory' | awk '{print $4;}' | grep -v '/' | sort | uniq | sed 's/.$//'.
If you have a fedora/redhat based system, bash has been patched with the --rpm-requires flag
--rpm-requires: Produce the list of files that are required for the shell script to run. This implies -n and is subject to the same limitations as compile time error checking checking; Command substitutions, Conditional expressions and eval builtin are not parsed so some dependencies may be missed.
So when you run the following:
$ bash --rpm-requires script.sh
executable(command1)
function(function1)
function(function2)
executable(command2)
function(function3)
There are some limitations here:
command and process substitutions and conditional expressions are not picked up. So the following are ignored:
$(command)
<(command)
>(command)
command1 && command2 || command3
commands as strings are not picked up. So the following line will be ignored
"/path/to/my/command"
commands that contain shell variables are not listed. This generally makes sense since
some might be the result of some script logic, but even the following is ignored
$HOME/bin/command
This point can however be bypassed by using envsubst and running it as
$ bash --rpm-requires <(<script envsubst)
However, if you use shellcheck, you most likely quoted this and it will still be ignored due to point 2
So if you want to use check if your scripts are all there, you can do something like:
while IFS='' read -r app; do
[ "${app%%(*}" == "executable" ] || continue
app="${app#*(}"; app="${app%)}";
if [ "$(type -t "${app}")" != "builtin" ] && \
! [ -x "$(command -v "${app}")" ]
then
echo "${app}: missing application"
fi
done < <(bash --rpm-requires <(<"$0" envsubst) )
If your script contains files that are sourced that might contain various functions and other important definitions, you might want to do something like
bash --rpm-requires <(cat source1 source2 ... <(<script.sh envsubst))
Based #czvtools’ answer, I added some extra checks to filter out bad values:
#!/usr/bin/fish
if test "$argv[1]" = ""
echo "Give path to command to be tested"
exit 1
end
set commands (cat $argv \
| sed -e 's/\"/./g' -e "s/'[^']*'//g" -e 's/"[^"]*"//g' \
| sed -e "s/^[[:space:]]*#.*\$//" -e "s/\([^\\]\)#[^\"']*\$/\1/" \
| sed -e "s/&&/;/g" -e "s/||/;/g" | tr ";|" "\n\n" \
| awk '{print $1}' | sort -u)
for command in $commands
if command -q -- $command
set -a resolved (realpath (which $command))
end
end
set resolved (string join0 $resolved | sort -z -u | string split0)
for command in $resolved
echo $command
end
I am monitoring the new files created in a folder in linux. Every now and then I issue an "ls -ltr" in it. But I wish there was a program/script that would automatically print it, and only the latest entries. I did a short while loop to list it, but it would repeat the entries that were not new and it would keep my screen rolling up when there were no new files. I've learned about "watch", which does show what I want and refreshes every N seconds, but I don't want a ncurses interface, I'm looking for something like tail:
continuous
shows only the new stuff
prints in my terminal, so I can run it in the background and do other things and see the output every now and then getting mixed with whatever I'm doing :D
Summarizing: get the input, compare to a previous input, output only what is new.
Something that do that doesn't sound like such an odd tool, I can see it being used for other situations also, so I would expect it to already exist, but I couldn't find anything. Suggestions?
You can use the very handy command watch
watch -n 10 "ls -ltr"
And you will get a ls every 10 seconds.
And if you add a tail -10 you will only get the 10 newest.
watch -n 10 "ls -ltr|tail -10"
If you have access to inotifywait (available from the inotify-tools package if you are on Debian/Ubuntu) you could write a script like this:
#!/bin/bash
WATCH=/tmp
inotifywait -q -m -e create --format %f $WATCH | while read event
do
ls -ltr $WATCH/$event
done
This is a one-liner that won't give you the same information that ls does, but it will print out the filename:
inotifywait -q -m -e create --format %w%f /some/directory
This works in cygwin and Linux. Some of the previous solutions which write a file will cause the disk to thrash.
This script does not have that problem:
SIG=1
SIG0=SIG
while [ $SIG != 0 ] ; do
while [ $SIG = $SIG0 ] ; do
SIG=`ls -1 | md5sum | cut -c1-32`
sleep 10
done
SIG0=$SIG
ls -lrt | tail -n 1
done
I want to run something along the lines of
vim -r -c "w %.new | q!" ${filename}
However, the ! is parsed as the prefix for an external command. Similar issues happen when using single quotes.
I could work around this with the following code, but it feels much less clean or obvious than the previous code.
cp ${filename} ${filename}.new && mv .${filename}.swp .${filename}.new.swp;
vim -r -c "wq" ${filename}.new;
Use single quotes instead of double quotes. The ! is being interpreted in bash not vim.
vim -r -c 'w %.new | q!' ${filename}
! followed by test runs the last command that starts with that text. In this case bash looks for a command starting with " which isn't found. The single quotes stops bash from interpreting the !
Some examples of using ! in bash
It seems the actual problem was that %.new existed. To just force over write use w! instead of w
vim -r -c 'w! %.new | q!' ${filename}
I want to tail multiple files (and follow them) in CentOS, I've tried this:
tail -f file1 file2 file3
but the output is very unfriendly
I've also had a look at multitail but can't find a CentOS version.
What other choices do I have?
Multitail is available for CentOS in rpmforge repos. To add rpmforge repository check the documentation on 3rd Party Repositories.
I found the solution described here work well on centos:
The link is http://www.thegeekstuff.com/2009/09/multitail-to-view-tail-f-output-of-multiple-log-files-in-one-terminal/
Thanks to Ramesh Natarajan
$ vi multi-tail.sh
#!/bin/sh
# When this exits, exit all back ground process also.
trap 'kill $(jobs -p)' EXIT
# iterate through the each given file names,
for file in "$#"
do
# show tails of each in background.
tail -f $file &
done
# wait .. until CTRL+C
wait
You could simulate multitail by opening multiple instances of tail -f in Emacs subwindows.
I usually just open another xterm and run a separate 'tail -f' there.
Otherwise if I'm using the 'screen' tool, I'll set up separate 'tail -f' commands there. I don't like that as much because it takes a few keystrokes to enable scrolling in screen before using the Page Up and Page Down keys. I prefer to just use xterm's scroll bar.
You can use the watch command, i use it to tail two files at the same time:
watch -n0 tail -n30 file1 file2
A better answer to an old question...
I create a shell function in my .bashrc (obviously assumes you're using bash as your shell) and use tmux. You can probably complicate this a whole lot and do it without the tempfile, but the quoting is just ugly if you're trying to ensure that files with spaces or other weird characters in the name still work.
multitail ()
{
cmdfile=`mktemp`
echo "new-session -d \"tail -f '$1'\"" >$cmdfile
shift
for file in "$#"
do
echo "split-window -d \"tail -f '$file'\"" >>$cmdfile
done
echo "select-layout even-vertical" >>$cmdfile
tmux source-file $cmdfile \; attach && rm -f $cmdfile
}