If I have sample_1.txt, sample_2.txt, sample_3.txt, sample_4.txt, and I want to perform a command line job repeatedly.
For example, instead of typing the same command four times like below, is there a command that could do that automatically?
$ grep 'pattern' sample_1.txt
$ grep 'pattern' sample_2.txt
$ grep 'pattern' sample_3.txt
$ grep 'pattern' sample_4.txt
Try this
$grep 'pattern' sample_1.txt sample_2.txt sample_3.txt sample_4.txt
And also can use simple bash script for command which not accept multipe input>>
#!/bin/bash
for i in $( ls ); do
grep "include" $i
done
Related
i wonder if there is a more simplyfied way to run the tail -f or -F on a logfile and execute a command each time a special keyword is mentioned.
this is my working solution so far, but i don't like it for following reasons:
i have to write new lines for each match to log file to avoid endless loop
tail does not follow exactly the log, it could miss some lines while the command is executed
i am not aware about CPU usage because of high frequency
example:
#!/sbin/sh
while [ 1 ]
do
tail -n1 logfile.log | grep "some triggering text" && mount -v $stuff >> logfile.log
done
i tried the following but grep won't give return code until the pipe break
#!/sbin/sh
tail -f -n1 logfile.log | grep "some triggering text" && mount $stuff
i am running a script on android which is limited to
busybox ash
edit:
the problem is related to grep. grep won't give return code until the last line. what i need is return code for each line. maybe kind of a --follow option for grep, or sed, awk, or a user defined function which works with tail --follow
I am trying to execute, what I thought would be, a simple shell command within a script. When I execute this from the command prompt, it works well:
$ sudo cat /etc/sysconfig/network-scripts/ifcfg-en0 | grep "IPADDR"
IPADDR=192.168.1.10
However, if I put this into a shell script:
#!/usr/bin/sh
my_command=`sudo cat /etc/sysconfig/network-scripts/ifcfg-en0 | grep "IPADDR"`
${my_command}
echo $?
I get this error:
$ sudo ./myscript.sh
./myscript.sh: line 3: IPADDR=192.168.1.10: command not found
So, how can I successfully execute this line within my shell script?
Thanks!
The problem in your case is that you are executing the result of the command...
This line executes the code as it's between "``" that are special characters for executing the given string as a command:
my_command=`sudo cat /etc/sysconfig/network-scripts/ifcfg-en0 | grep "IPADDR"`
as a result, $my_command is "IPADDR=192.168.1.10"
Then you are trying to execute it for the second time:
${my_command}
Thats why you are getting this error. There is no such a command as "IPADDR=192.168.1.10".
Just use $my_command as a result that contains your desired grepped part and skip the ${my_command} line:
#!/usr/bin/sh
my_command=`sudo cat /etc/sysconfig/network-scripts/ifcfg-en0 | grep "IPADDR"`
echo $my_command
If multiple arguments are passed to perl's system function then the shell expansion will not work:
# COMMAND
$ perl -e 'my $s="*"; system("echo", "$s" )'
# RESULT
*
If the command is passed as an one argument then the expansion will work:
# COMMAND
$ perl -e 'my $s="echo *"; system("$s")'
# RESULT
Desktop Documents Downloads
The system function also allows to using multiple commands and connect them using pipes. This only works when argument is passed as an one command:
# COMMAND
$ perl -e 'my $s="echo * | cat -n"; system("$s")'
# RESULT
1 Desktop Documents Downloads
How can I combine mentioned commands and use both pipes and prevent shell expansion?
I have tried:
# COMMAND
$ perl -e 'my $s="echo"; system("$s", "* | cat -n")'
# RESULT
* | cat -n
but this did not work because of reasons that I've described above (multiple arguments are not expanded). The result that I want is:
1 *
EDIT:
The problem that I'm actually facing is that when I use following command:
system("echo \"$email_message\" | mailx -s \"$email_subject\" $recipient");
Then the $email_message is expanded and it will break mailx if it contains some characters that are further expanded by shell.
system has three calling conventions:
system($SHELL_CMD)
system($PROG, #ARGS) # #ARGS>0
system( { $PROG } $NAME, #ARGS ) # #ARGS>=0
The first passes a command to the shell. It's equivalent to
system('/bin/sh', '-c', $SHELL_CMD)
The other two execute the program $PROG. system never prevents shell expansion or performs any escaping. There's simply no shell involved.
So your question is about building a shell command. If you were at the prompt, you might use
echo \* | cat -n
or
echo '*' | cat -n
to pass *. You need a function that performs the job of escaping * before interpolating it. Fortunately, one already exists: String::ShellQuote's shell_quote.
$ perl -e'
use String::ShellQuote qw( shell_quote );
my $s = "*";
my $cmd1 = shell_quote("printf", q{%s\n}, $s);
my $cmd2 = "cat -n";
my $cmd = "$cmd1 | $cmd2";
print("Executing <<$cmd>>\n");
system($cmd);
'
Executing <<printf '%s\n' '*' | cat -n>>
1 *
I used printf instead of echo since it's very hard to handle arguments starting with - in echo. Most programs accept -- to separate options from non-options, but not my echo.
All these complications beg the question: Why are you shelling out to send an email? It's usually much harder to handle errors from external programs than from libraries.
You can use open to pipe directly to mailx, without your content being interpreted by the shell:
open( my $mail, "|-", "mailx", "-s", $email_subject, $recipient );
say $mail $email_message;
close $mail;
More details can be found in open section of perlipc.
I just blindly followed a command from a tutorial to rename several folders at a time. Can anyone explain the meaning of "p;s" given as the argument to sed's -e option.
[root#LinuxD delsure]# ls
ar1 ar2 ar3 ar4 ar5 ar6 ar7
[root#LinuxD delsure]# find . -type d -name "ar*"|sed -e "p;s/ar/AR/g"|xargs -n2 mv
[root#LinuxD delsure]# ls
AR1 AR2 AR3 AR4 AR5 AR6 AR7
A sed script (the bit following the -e option) can contain multiple commands, separated by ;
The script in your example uses the p command to print the pattern space (i.e. the line just read from the input) followed by the s command to perform a substitution on the pattern space.
By default (unless the pattern space is cleared or the -n option is given to sed) after processing each line the current pattern spaceline is printed again, so the result of the substitution will be printed.
Another way to write the same thing would be:
sed -e "p" -e "s/ar/AR/g"
This separates the commands into two scripts. Another way would be:
sed "p;s/ar/AR/g"
because if the only argument to sed is a script then the -e option is not needed
The argument to the -e option is a script consisting of two commands. The first is p, which prints the unadulterated input, the second is a standard, global substitution. So for input ar1, this should output
ar1
AR1
The other part of this trick is the -n2 option on xargs, which forces it to only use two arguments at a time (instead of as many as it can handle, which would produce very different results).
One way in bash:
$ ls
ar6 ar7
$ find . -name 'ar*' | while IFS= read -r file; do echo mv "$file" "${file^^}"; done
mv ./ar6 ./AR6
mv ./ar7 ./AR7
get rid of the "echo" when you're happy with the output.
I'm trying to run a perl script from within a bash script (I'll change this design later on, but for now, bear with me). The bash script receives the argument that it will run. The argument to the script is as follows:
test.sh "myscript.pl -g \"Some Example\" -n 1 -p 45"
within the bash script, I simple run the argument that was passed:
#!/bin/sh
$1
However, in my perl script the -g argument only gets "Some (that's with the quotes), instead of the Some Example. Even if I quote it, it cuts off because of the whitespace.
I tried escaping the whitespace, but it doesn't work... any ideas?
To run it as posted test.sh "myscript.pl -g \"Some Example\" -n 1 -p 45" do this:
#!/bin/bash
eval "$1"
This causes the $1 argument to be parsed by the shell so the individual words will be broken up and the quotes removed.
Or if you want you could remove the quotes and run test.sh myscript.pl -g "Some Example" -n 1 -p 45 if you changed your script to:
#!/bin/bash
"$#"
The "$#" gets replaced by all the arguments $1, $2, etc., as many as were passed in on the command line.
Quoting is normally handled by the parser, which isn't seeing them when you substitute the value of $1 in your script.
You may have more luck with:
#!/bin/sh
eval "$1"
which gives:
$ sh test.sh 'perl -le "for (#ARGV) { print; }" "hello world" bye'
hello world
bye
Note that simply forcing the shell to interpret the quoting with "$1" won't work because then it tries to treat the first argument (i.e., the entire command) as the name of the command to be executed. You need the pass through eval to get proper quoting and then re-parsing of the command.
This approach is (obviously?) dangerous and fraught with security risks.
I would suggest you name the perl script in a separate word, then you can quote the parameters when referring to them, and still easily extract the script name without needing the shell to split the words, which is the fundamental problem you have.
test.sh myscript.pl "-g \"Some Example\" -n 1 -p 45"
and then
#!/bin/sh
$1 "$2"
if you really have to do this (for whatever reason) why not just do:
sh test.sh "'Some Example' -n 1 -p 45"
in:
test.sh
RUN=myscript.pl
echo `$RUN $1
(there should be backticks ` before $RUN and after $1)