I did check the ABS, but it was hard to find a reference to my problem/question there.
Here it is. Consider the following code (Which extracts the first character of OtherVar and then converts MyVar to uppercase):
OtherVar=foobar
MyChar=${OtherVar:0:1} # get first character of OtherVar string variable
MyChar=${MyChar^} # first character to upper case
Could I somehow condense the second and third line into one statement?
P.S.: As was pointed out below, not needs to have a named variable. I should add, I would like to not add any sub-shells or so and would also accept a somehow hacky way to achieve the desired result.
P.P.S.: The question is purely educational.
You could do it all-in-one without forking sub-shell or running external command:
printf -v MyChar %1s "${OtherVar^}"
Or:
read -n1 MyChar <<<"${OtherVar^}"
Another option:
declare -u MyChar=${OtherVar:0:1}
But I can't see the point in such optimization in a bash script.
There are more suitable text processing interpreters, like awk, sed, even perl or python if performance matters.
You could use the cut command and put it in a complex expression to get it on one line, but I'm not sure it makes the code too much clearer:
OtherVar=foobar
MyChar=$(echo ${OtherVar^} | cut -c1-1) # uppercase first character and cut string
Related
I have a shell script where I have a statement:
isPartial = $searchCurl| grep -Po '\"partialSearch\":(true|false)'|sed 's/\\\"partialSearch\\\"://'
now, if I just echo the RHS
$searchCurl| grep -Po '\"partialSearch\":(true|false)'|sed 's/\\\"partialSearch\\\"://'
it prints "partialSearch":true, but the variable isPartial doesn't get initialized .
Why is this happening and how can I fix it ?
Since the number of backslashes in your examples varies, it is not clear to me if the double quotes are already escaped in the input text. I’ll assume they are not, i.e. the input text looks something like:
sometext... "partialSearch":true ... sometext...
..bla bla bla... "partialsearch":false ...
and my examples below will work under this assumption.
There are a number of points to be made.
You seem to be trying to parse JSON input with regular expressions. While this could be acceptable for quick-and-dirty one-time jobs where you know the exact format of the data being processed, in general it is a very bad idea. You should use a JSON parser like jq.
You obviously have stored some bash code in the variable searchCurl. This is considered bad practice. Instead of searchCurl="... code ..." you should do function searchCurl () { ... code ... } and call searchCurl without prefixing it with a dollar sign. Variables are for values, functions are for code.
In most cases, if you are going to use sed, it’s better to use it for everything without invoking grep. Sometimes it can be simpler to have both. See below for an example.
To assign the output of a command to a variable, you have to use command substitution.
In short, if in your input text you have only one match of '"partialSearch":(true|false)', this is what you want:
isPartial=$(searchCurl|sed -rn 's/^.*"partialSearch":(true|false).*$/\1/p')
If you have more and the input text is one big line as I suppose, usage of grep -o might simplify the task of splitting the input into one match per line, so that
isPartial=$(searchCurl|grep -Po '"partialSearch":(true|false)'|sed -e 's/^.*://')
might be what you want (and in this case, isPartial will hold a space-separated list of true and false).
Before to write, of course I read many other similar cases. Example I used #!/bin/bash instead of #!/bin/sh
I have a very simple script that reads lines from a template file and wants to replace some keywords with real data. Example the string <NAME> will be replaced with a real name. In the example I want to replace it with the word Giuseppe. I tried 2 solutions but they don't work.
#!/bin/bash
#read the template and change variable information
while read LINE
do
sed 'LINE/<NAME>/Giuseppe' #error: sed: -e expression #1, char 2: extra characters after command
${LINE/<NAME>/Giuseppe} #error: WORD(*) command not found
done < template_mail.txt
(*) WORD is the first word found in the line
I am sorry if the question is too basic, but I cannot see the error and the error message is not helping.
EDIT1:
The input file should not be changed, i want to use it for every mail. Every time i read it, i will change with a different name according to the receiver.
EDIT2:
Thanks your answers i am closer to the solution. My example was a simplified case, but i want to change also other data. I want to do multiple substitutions to the same string, but BASH allows me only to make one substitution. In all programming languages i used, i was able to substitute from a string, but BASH makes this very difficult for me. The following lines don't work:
CUSTOM_MAIL=$(sed 's/<NAME>/Giuseppe/' template_mail.txt) # from file it's ok
CUSTOM_MAIL=$(sed 's/<VALUE>/30/' CUSTOM_MAIL) # from variable doesn't work
I want to modify CUSTOM_MAIL a few times in order to include a few real informations.
CUSTOM_MAIL=$(sed 's/<VALUE1>/value1/' template_mail.txt)
${CUSTOM_MAIL/'<VALUE2>'/'value2'}
${CUSTOM_MAIL/'<VALUE3>'/'value3'}
${CUSTOM_MAIL/'<VALUE4>'/'value4'}
What's the way?
No need to do the loop manually. sed command itself runs the expression on each line of provided file:
sed 's/<NAME>/Giuseppe/' template_mail.txt > output_file.txt
You might need g modifier if there are more appearances of the <NAME> string on one line: s/<NAME>/Giuseppe/g
I am currently trying to install GCC-4.1.2 on my machine: Fedora 20.
In the instruction, the first three commands involve using 'sed' commands, for Makefile modification. However, I am having difficulty in using those commands properly for my case. The website link for GCC-4.1.2.
The commands are:
sed -i 's/install_to_$(INSTALL_DEST) //' libiberty/Makefile.in &&
sed -i 's#\./fixinc\.sh#-c true#' gcc/Makefile.in &&
sed -i 's/#have_mktemp_command#/yes/' gcc/gccbug.in &&
I am trying to understand them by reading the 'sed' man page, but it is not so easy to do so. Any help/tip would be appreciated!
First, the shell part: &&. That just chains the commands together, so each subsequent line will only be run if the prior one is run successfully.
sed -i means "run these commands inline on the file", that is, modify the file directly instead of printing the changed contents to STDOUT. Each sed command here (the string) is a substitute command, which we can tell because the command starts with s.
Substitute looks for a piece of text in the file, and then replaces it. So the order is always s/needle/replacement/. See how the first and last lines have those same forward-slashes? That's the traditional delimiter between the command (substitute), the needle to find in the haystack (install_to_$(INSTALL_DEST), and the text to replace it with ().
So, the first one looks for the string and deletes it (the empty replacement). The last one looks for #have_mktemp_command# and replaces it with yes.
The middle one is a bit weird. See how it starts with s# instead of s/? Well, sed will let you use any delimiter you like to separate the needle from the replacement. Since this needle had a / in it (\./fixinc\.sh), it made sense to use a different delimiter than /. It will replace the text ./fixinc.sh with -c true.
Last note: Why does the second needle have \. instead of .? Well, in a Regular Expression like the needle is (but not used in your example), some characters are magical and do magical fairy dust operations. One of those magic characters is .. To avoid the magic, we put a \ in front of it, escaping away from the magic. (The magic is "match any character", and we want a literal period. That's why.)
I'm trying to strip the version out of a package name using only Bash. I have one solution but I don't think that's the best one available, so I'd like to know if there's a better way to do it. by better I mean cleaner, easier to understand.
suppose I have the string "my-program-1.0" and I want only "my-program". my current solution is:
#!/bin/bash
PROGRAM_FULL="my-program-1.0"
INDEX_OF_LAST_CHARACTER=`awk '{print match($0, "[A-Za-z0-9]-[0-9]")} <<< $PROGRAM_FULL`
PROGRAM_NAME=`cut -c -$INDEX_OF_LAST_CHARACTER <<< $PROGRAM_FULL`
actually, the "package name" syntax is an RPM file name, if it matters.
thanks!
Pretty well-suited to sed:
# Using your matching criterion (first hyphen with a number after it
PROGRAM_NAME=$(echo "$PROGRAM_FULL" | sed 's/-[0-9].*//')
# Using a stronger match
PROGRAM_NAME=$(echo "$PROGRAM_FULL" | sed 's/-[0-9]\+\(\.[0-9]\+\)*$//')
The second match ensures that the version number is a sequence of numbers separated by dots (e.g. X, X.X, X.X.X, ...).
Edit: So there are comments all over based on the fact that the notion of version number isn't very well-defined. You'll have to write a regex for the input you expect. Hopefully you won't have anything as awful as "program-name-1.2.3-a". Absent any additional request from the OP though, I think all the answers here are good enough.
Bash:
program_full="my-program-1.0"
program_name=${program_full%-*} # remove the last hyphen and everything after
Produces "my-program"
Or
program_full="alsa-lib-1.0.17-1.el5.i386.rpm"
program_name=${program_full%%-[0-9]*} # remove the first hyphen followed by a digit and everything after
Produces "alsa-lib"
How about:
$ echo my-program-1.0 | perl -pne 's/-[0-9]+(\.[0-9]+)+$//'
my-program
I am writing a shell (bash) script and I'm trying to figure out an easy way to accomplish a simple task.
I have some string in a variable.
I don't know if this is relevant, but it can contain spaces, newlines, because actually this string is the content of a whole text file.
I want to replace the last occurence of a certain substring with something else.
Perhaps I could use a regexp for that, but there are two moments that confuse me:
I need to match from the end, not from the start
the substring that I want to scan for is fixed, not variable.
for truncating at the start: ${var#pattern}
truncating at the end ${var%pattern}
${var/pattern/repl} for general replacement
the patterns are 'filename' style expansion, and the last one can be prefixed with # or % to match only at the start or end (respectively)
it's all in the (long) bash manpage. check the "Parameter Expansion" chapter.
amn expression like this
s/match string here$/new string/
should do the trick - s is for sustitute, / break up the command, and the $ is the end of line marker. You can try this in vi to see if it does what you need.
I would look up the man pages for awk or sed.
Javier's answer is shell specific and won't work in all shells.
The sed answers that MrTelly and epochwolf alluded to are incomplete and should look something like this:
MyString="stuff ttto be edittted"
NewString=`echo $MyString | sed -e 's/\(.*\)ttt\(.*\)/\1xxx\2/'`
The reason this works without having to use the $ to mark the end is that the first '.*' is greedy and will attempt to gather up as much as possible while allowing the rest of the regular expression to be true.
This sed command should work fine in any shell context used.
Usually when I get stuck with Sed I use this page,
http://sed.sourceforge.net/sed1line.txt