might be an easy question, I'm new in bash and haven't been able to find the solution to my question.
I'm writing the following script:
for file in `ls *.map`; do
ID=${file%.map}
convertf -p ${ID}_par #this is a program that I use, no problem
NAME=head -n 1 ${ID}.ind | cut -f1 -d":" #Now: This step is the problem: don't seem to be able to make a proper NAME function. I just want to take the first column of the first line of the file ${ID}.ind
It gives me the return
line 5: bad substitution
any help?
Thanks!
There are a couple of issues in your code:
for file in `ls *.map` does not do what you want. It will fail e.g. if any of the filenames contains a space or *, but there's more. See http://mywiki.wooledge.org/BashPitfalls#for_i_in_.24.28ls_.2A.mp3.29 for details.
You should just use for file in *.map instead.
ALL_UPPERCASE names are generally used for system variables and built-in shell variables. Use lowercase for your own names.
That said,
for file in *.map; do
id="${file%.map}"
convertf -p "${id}_par"
name="$(head -n 1 "${id}.ind" | cut -f1 -d":")"
...
looks like it would work. We just use $( cmd ) to capture the output of a command in a string.
Related
I'm trying to temporarily disable dhcp on all connections in a computer using bash, so I need the process to be reversible. My approach is to comment out lines that contain BOOTPROTO=dhcp, and then insert a line below it with BOOTPROTO=none. I'm not sure of the correct syntax to make sed understand the line number stored in the $insertLine variable.
fileList=$(ls /etc/sysconfig/network-scripts | grep ^ifcfg)
path="/etc/sysconfig/network-scripts/"
for file in $fileList
do
echo "looking for dhcp entry in $file"
if [ $(cat $path$file | grep ^BOOTPROTO=dhcp) ]; then
echo "disabling dhcp in $file"
editLine=$(grep -n ^BOOTPROTO=dhcp /$path$file | cut -d : -f 1 )
#comment out the original dhcp value
sed -i "s/BOOTPROTO=dhcp/#BOOTPROTO=dhcp/g" $path$file
#insert a line below it with value of none.
((insertLine=$editLine+1))
sed "$($insertLine)iBOOTPROTO=none" $path$file
fi
done
Any help using sed or other stream editor greatly appreciated. I'm using RHEL 6.
The sed editor should be able to do the job, without having to to be combine bash, grep, cat, etc. Easier to test, and more reliable.
The whole scripts can be simplified to the below. It performs all operations (substitution and the insert) with a single pass using multiple sed scriptlets.
#! /bin/sh
for file in $(grep -l "^BOOTPROTO=dhcp" /etc/sysconfig/network-scripts/ifcfg*) ; do
sed -i -e "s/BOOTPROTO=dhcp/#BOOTPROTO=dhcp/g" -e "/BOOTPROTO=dhcp/i BOOTPROTO=none" $file
done
As side note consider NOT using path as variable to avoid possible confusion with the 'PATH` environment variable.
Writing it up, your attempt with the following fails:
sed "$($insertLine)iBOOTPROTO=none" $path$file
because:
$($insertLine) encloses $insertLIne in a command substitution which when $insertLIne is evaluated it returns a number which is not a command generating an error.
your call to sed does not include the -i option to edit the file $path$file in place.
You can correct the issues with:
sed -i "${insertLine}i BOOTPROTO=none" $path$file
Which is just sed - i (edit in place) and Ni where N is the number of the line to insert followed by the content to insert and finally what file to insert it in. You add ${..} to insertLine to protect the variable name from the i that follows and then the expression is double-quoted to allow variable expansion.
Let me know if you have any further questions.
(and see dash-o's answer for refactoring the whole thing to simply use sed to make the change without spawning 10 other subshells)
So I want to automate a manual task using shell scripting, but I'm a little lost as to how to parse the output of a few commands. I would be able to this in other languages without a problem, so I'll just explain what I'm going for in psuedo code and provide an example of the cmd output I'm trying to parse.
Example of output:
Chg 2167467 on 2012/02/13 by user1234#filename 'description of submission'
What I need to parse out is '2167467'. So what I want to do is split on spaces and take element 1 to use in another command. The output of my next command looks like this:
Change 2167463 by user1234#filename on 2012/02/13 18:10:15
description of submission
Affected files ...
... //filepath/dir1/dir2/dir3/filename#2298 edit
I need to parse out '//filepath/dir1/dir2/dir3/filename#2298' and use that in another command. Again, what I would do is remove the blank lines from the output, grab the 4th line, and split on space. From there I would grab the 1st element from the split and use it in my next command.
How can I do this in shell scripting? Examples or a point to some tutorials would be great.
Its not clear if you want to use the result from the first command for processing the 2nd command. If that is true, then
targString=$( cmd1 | awk '{print $2}')
command2 | sed -n "/${targString}/{n;n;n;s#.*[/][/]#//#;p;}"
Your example data has 2 different Chg values in it, (2167467, 2167463), so if you just want to process this output in 2 different ways, its even simpler
cmd1 | awk '{print $2}'
cmd2 | sed -n '/Change/{n;n;n;s#.*[/][/]#//#;p;}'
I hope this helps.
I'm not 100% clear on your question, but I would use awk.
http://www.cyberciti.biz/faq/bash-scripting-using-awk/
Your first variable would look something like this
temp="Chg 2167467 on 2012/02/13 by user1234#filename 'description of submission'"
To get the number you want do this:
temp=`echo $temp | cut -f2 -d" "`
Let the output of your second command be saved to a file something like this
command $temp > file.txt
To get what you want from the file you can run this:
temp=`tail -1 file.txt | cut -f2 -d" "`
rm file.txt
The last block of code gets the last nonwhite line of the file and delimits on the second set of white spaces
Let's say that during your workday you repeatedly encounter the following form of columnized output from some command in bash (in my case from executing svn st in my Rails working directory):
? changes.patch
M app/models/superman.rb
A app/models/superwoman.rb
in order to work with the output of your command - in this case the filenames - some sort of parsing is required so that the second column can be used as input for the next command.
What I've been doing is to use awk to get at the second column, e.g. when I want to remove all files (not that that's a typical usecase :), I would do:
svn st | awk '{print $2}' | xargs rm
Since I type this a lot, a natural question is: is there a shorter (thus cooler) way of accomplishing this in bash?
NOTE:
What I am asking is essentially a shell command question even though my concrete example is on my svn workflow. If you feel that workflow is silly and suggest an alternative approach, I probably won't vote you down, but others might, since the question here is really how to get the n-th column command output in bash, in the shortest manner possible. Thanks :)
You can use cut to access the second field:
cut -f2
Edit:
Sorry, didn't realise that SVN doesn't use tabs in its output, so that's a bit useless. You can tailor cut to the output but it's a bit fragile - something like cut -c 10- would work, but the exact value will depend on your setup.
Another option is something like: sed 's/.\s\+//'
To accomplish the same thing as:
svn st | awk '{print $2}' | xargs rm
using only bash you can use:
svn st | while read a b; do rm "$b"; done
Granted, it's not shorter, but it's a bit more efficient and it handles whitespace in your filenames correctly.
I found myself in the same situation and ended up adding these aliases to my .profile file:
alias c1="awk '{print \$1}'"
alias c2="awk '{print \$2}'"
alias c3="awk '{print \$3}'"
alias c4="awk '{print \$4}'"
alias c5="awk '{print \$5}'"
alias c6="awk '{print \$6}'"
alias c7="awk '{print \$7}'"
alias c8="awk '{print \$8}'"
alias c9="awk '{print \$9}'"
Which allows me to write things like this:
svn st | c2 | xargs rm
Try the zsh. It supports suffix alias, so you can define X in your .zshrc to be
alias -g X="| cut -d' ' -f2"
then you can do:
cat file X
You can take it one step further and define it for the nth column:
alias -g X2="| cut -d' ' -f2"
alias -g X1="| cut -d' ' -f1"
alias -g X3="| cut -d' ' -f3"
which will output the nth column of file "file". You can do this for grep output or less output, too. This is very handy and a killer feature of the zsh.
You can go one step further and define D to be:
alias -g D="|xargs rm"
Now you can type:
cat file X1 D
to delete all files mentioned in the first column of file "file".
If you know the bash, the zsh is not much of a change except for some new features.
HTH Chris
Because you seem to be unfamiliar with scripts, here is an example.
#!/bin/sh
# usage: svn st | x 2 | xargs rm
col=$1
shift
awk -v col="$col" '{print $col}' "${#--}"
If you save this in ~/bin/x and make sure ~/bin is in your PATH (now that is something you can and should put in your .bashrc) you have the shortest possible command for generally extracting column n; x n.
The script should do proper error checking and bail if invoked with a non-numeric argument or the incorrect number of arguments, etc; but expanding on this bare-bones essential version will be in unit 102.
Maybe you will want to extend the script to allow a different column delimiter. Awk by default parses input into fields on whitespace; to use a different delimiter, use -F ':' where : is the new delimiter. Implementing this as an option to the script makes it slightly longer, so I'm leaving that as an exercise for the reader.
Usage
Given a file file:
1 2 3
4 5 6
You can either pass it via stdin (using a useless cat merely as a placeholder for something more useful);
$ cat file | sh script.sh 2
2
5
Or provide it as an argument to the script:
$ sh script.sh 2 file
2
5
Here, sh script.sh is assuming that the script is saved as script.sh in the current directory; if you save it with a more useful name somewhere in your PATH and mark it executable, as in the instructions above, obviously use the useful name instead (and no sh).
It looks like you already have a solution. To make things easier, why not just put your command in a bash script (with a short name) and just run that instead of typing out that 'long' command every time?
If you are ok with manually selecting the column, you could be very fast using pick:
svn st | pick | xargs rm
Just go to any cell of the 2nd column, press c and then hit enter
Note, that file path does not have to be in second column of svn st output. For example if you modify file, and modify it's property, it will be 3rd column.
See possible output examples in:
svn help st
Example output:
M wc/bar.c
A + wc/qax.c
I suggest to cut first 8 characters by:
svn st | cut -c8- | while read FILE; do echo whatever with "$FILE"; done
If you want to be 100% sure, and deal with fancy filenames with white space at the end for example, you need to parse xml output:
svn st --xml | grep -o 'path=".*"' | sed 's/^path="//; s/"$//'
Of course you may want to use some real XML parser instead of grep/sed.
I am trying to automate the copying of changed files into a perforce changelist, but need help getting the generated changelist number. I assume this is probably a straight-forward thing for bash scripting - but I'm just not getting it yet!!...
Basically I execute the command
p4 change -o | sed 's/<enter description here>/This is my description./' | p4 change -i
As a result of this, I get output onto screen something like the line below (obviously the number changes)
Change 44152 created.
What I want, is to be able to capture the generated number into a variable I can then use in the rest of my script (to add future files to the same changelist etc)...
Can anyone please advise?
Thanks
like this
change=`p4 change -o | sed 's/<enter description here>/This is my description./' | p4 change -i|cut -d f2`
echo $change
EDIT: Per #Enigma last comment
If you want to use shell variable in sed command use doublr quote "" instead single quote '' around sed command. Like below
sed "s/<enter description here>/ updating $change form/"
Results in "updating 44152 form" ($change holds value 44152)
You can capture the output of a command with the ` character.
myVariable=`myCommand`
You can use awk to get the 2nd column of data, the number part.
myVariable=`originalCommand|awk '{print $2}'`
Now myVariable will be your number, 44152.
you could use cut. Here is another related stackoverflow entry:
use space as a delimiter with cut command
I would use something like this
echo "Change 44152 created." | tr -d 'a-zA-Z .'
If you are wanting to get the last generated changelist, you can also type
variable=`p4 counter change`
but this will only work if no one else made a changelist after you made yours.
Is there a way to grab a 'random matching' string via bash from a text file?
I am currently grabbing a download link via bash, curl & grep from a online text file.
Example:
DOWNLOADSTRING="$(curl -o - "http://example.com/folder/downloadlinks.txt" | grep "$VARIABLE")"
from online text file which contains
http://alphaserver.com/files/apple.zip
http://alphaserver.com/files/banana.zip
where $VARIABLE is something the user selected.
Works great, but i wanted to add some mirrors to the text file.
So when the variable 'banana' is selected, text file which i grep contains:
http://alphaserver.com/files/apple.zip
http://betaserver.com/files/apple.zip
http://gammaserver.com/files/apple.zip
http://deltaserver.com/files/apple.zip
http://alphaserver.com/files/banana.zip
http://betaserver.com/files/banana.zip
http://gammaserver.com/files/banana.zip
http://deltaserver.com/files/banana.zip
the code should pick a random 'banana' string and store it as the 'DOWNLOADSTRING' variable.
the current code above can only work with 1 string in the text file, since it grabs everything 'banana'.
What this is for; i wanted to add some mirror downloadlinks for the files in the online text file, and the current code doesn't allow that.
Can i let grep grab one random 'banana' string? (and not all of them)
See this question to see how to get a random line after grep. rl seems like a good candidate
What's an easy way to read random line from a file in Unix command line?
then do a grep ... | rl | head -n 1
Try this:
DOWNLOADSTRING="$(curl -o - "http://example.com/folder/downloadlinks.txt" | grep "$VARIABLE")" |
sort -R | head -1
The output will be random-sorted and then the first line will be selected.
If mirrors.txt has the following data, which you provided in your question:
http://alphaserver.com/files/apple.zip
http://betaserver.com/files/apple.zip
http://gammaserver.com/files/apple.zip
http://deltaserver.com/files/apple.zip
http://alphaserver.com/files/banana.zip
http://betaserver.com/files/banana.zip
http://gammaserver.com/files/banana.zip
http://deltaserver.com/files/banana.zip
Then you can use the following command to get a random "matched string" from the file:
grep -E "${VARIABLE}" mirrors.txt | shuf -n1
Then you can store it as the variable DOWNLOADSTRING by setting it's value with a function call like so:
rand_mirror_call() { grep -E "${1}" mirrors.txt | shuf -n1; }
DOWNLOADSTRING="$(rand_mirror_call ${VARIABLE})"
This will give you a dedicated random line from the text file based on the user's ${VARIABLE} input. It is a lot less typing this way.