This question already has answers here:
How to concatenate string variables in Bash
(30 answers)
Filename not printing correctly with underscore "_" in Bash [duplicate]
(2 answers)
Closed 4 years ago.
I'm trying to concatenate two variables in linux tectia SSH into one variable, separated by "_". For some reason only one of the two variables is printed out.
I've tried to concatenate via " " e.g.:
sample1="$var1_$var2"
or
sample1="$var1 _ $var2"
and I've tried to concatenate directly e.g.:
sample1=$var1_$var2
Would appreciate any help given!
cnt_abr1=ab
cnt_abr2=cd
cnt_abr3=ef
env_abr1=a
env_abr2=b
sample1="$env_abr1_$cnt_abr1"
sample2=$env_abr2_$cnt_abr3
echo $sample1
echo $sample2
Output:
_ ab
ef
Since underscores are effectively letters, bash has no way of knowing when your variable name ends and your literal underscore begins. The proper way to reference the variables is with ${...} in this case, which unambiguously delimits the name from the rest of the command line:
sample1="${env_abr1}_${cnt_abr1}"
sample2=${env_abr2}_${cnt_abr3}
In both cases, the second name does not require special treatment. Any other (semantically valid) non-letter character would do as well, as you pointed out in your comment:
sample1="$env_abr1"_"$cnt_abr1"
sample2="$env_abr2"_"$cnt_abr3"
Related
This question already has answers here:
How can I remove all text after a character in bash?
(7 answers)
Closed last month.
Working on a script where I need to take a string, and remove everything after the last occurence of a certain character. In this case a hyphen.
For example, This-is-a-filename-0001.jpg should result in This-is-a-filename
You can cut strings in bash:
line="This-is-a-filename-0001.jpg"
echo "${line%-*}" # prints: This-is-a-filename
The %-*operator removes all beginning with the last hyphen.
You're looking for a sed within your script, something close to what's below.
sed 's!/[^/]*$!/!'
Generally, I would say, please do research before posting a question like yours since it's relatively easy to find the answers
This question already has answers here:
What is the meaning of the ${0##...} syntax with variable, braces and hash character in bash?
(4 answers)
What does "##" in a shell script mean? [duplicate]
(1 answer)
Closed 7 months ago.
I came across a shell script like the following:
for FILE_PATH in `ls some/directory`
do
export FILE=${FILE_PATH##*/}
done
What exactly is the "##*/" doing? When I echo ${FILE} and ${FILE_PATH}, I don't see any difference. Is this to handle unusually named files?
More generally, how would I go about figuring out this type of question for myself in the future? Google was completely useless.
It's removing everything up to the last / in the value of $FILE. From the Bash Manual:
${parameter#word}
${parameter##word}
The word is expanded to produce a pattern and matched according to the rules described below (see Pattern Matching). If the pattern matches the beginning of the expanded value of parameter, then the result of the expansion is the value of parameter with the shortest matching pattern (the ‘#’ case) or the longest matching pattern (the ‘##’ case) deleted.
You're not seeing any difference in this case because when you list a directory it just outputs the filenames, it doesn't include the directory portion, so there's nothing to remove. You would see the difference if you did:
for FILE in some/directory/*
This question already has answers here:
How can I remove the ANSI escape sequences from a string in python
(8 answers)
Closed 3 years ago.
I am looking to format text before passing it to stdout/console. To do this properly I need to know how long a given section of text is after being printed to the console, which requires knowing how much characters will not be printed due to them being escape sequences.
On the web I have found multiple documentations for these sequence commands, but there seems to be no quick and easy way to find out where a given escape sequence command ends unless I was to parse them. Is there a trick/solution to getting the length of any escape sequence command without parsing?
How many characters is this \x1b[38;2;20;60;122m string \x1b[0m in console?
You can use ansifilter:
$ printf '\x1b[38;2;20;60;122mabc\x1b[0m' | ./ansifilter --no-trailing-nl | wc -c
3
This question already has answers here:
How to get a substring after the last underscore (_) in unix shell script
(3 answers)
Closed 3 years ago.
I have a string like:
arn:aws:ecs:us-east-1:123456789:task-definition/myservice:10
Is there anyway I can get the last value 10? I tried to get last character but forgot that this int value can increase and eventually becomes 2 characters.
Well, many ways, this one works, though is not elegant :)
echo "arn:aws:ecs:us-east-1:123456789:task-definition/myservice:10" | sed 's/.*://'
This question already has answers here:
Closed 10 years ago.
Possible Duplicate:
Python: Split string with multiple delimiters
Convert django Charfield “\t” to tab
I have written a python code in Eclipse which takes delimiters as an argument. When I do
print "Hello",delimiter, "All".
This generates --> Hello \t All, whereas if I overwrite the delimiter with delimiter = '\t' within the code, I get the right output Hello All. I wonder what is the difference? I hope this not just the eclipse thing.
The problem is that what is being passed in from the command line is actually a string of length two "\\t" and not a tab character. You can do the following to your delimiter
delimiter.decode("string_escape"))
that should convert the string '\\t' into '\t'. The answer comes from a duplicate questions here