Bash – extracting “tag” information from git with a shell script

awkbashgit

The vc bundle is a neat little package that extracts information about a git repo for easy insertion into a LaTeX document. It doesn't currently extract information about whether the current commit is tagged and what the tag name is. How would I edit the vc script to do this?

And then how would I edit the vc-git.awk script to add an extra line to the generated vc.tex file? Presumably I want a line that looks like:

print "\\gdef\\GITTag{" Tag "}%"

but I need an earlier line that tells awk what " Tag " means?

This isn't a question about LaTeX, it is about git, awk and bash…

Best Answer

git log --decorate -1 [commit]

If commit (HEAD if omitted) has tags, the commit hash will be followed by (tag: name) (and possibly multiple other symbolic references too). You can pick this out more specifically with

git log --pretty=%d

Related Solutions

Bash – How to pass output of one command as an argument to another

First, you need to massage the git branch output into a useable format

$ git branch
  experiment
* master
  new feature

$ git branch | awk '/^\* / { print $2 }'
master

Now, you want to use that as an argument:

$ git pull --rebase origin $(git branch | awk '/^\* / { print $2 }')

(or you can use backticks as in psusi's answer).

This should be ok, the awk command should always match exactly one line, and I'm assuming you can't have spaces in branch names. For anything much more complicated, I'd probably wrap it into a function (or a script) so you can do some sanity checking on the intermediate values.

Bash – Script that Outputs the Average of Multiple Group lines, from a File

Since awk arrays are indexed by strings, you can use one array to keep the total price for that brand so far, and use another array to keep the count of records seen for that brand.

Because "brand" is field 4, you can index the arrays in awk like this:

total_price[$4] += $3        # accumulate total price for this brand
count[$4] += 1               # increment count of records for this brand

At the end, loop through the keys to the arrays, and format the output while calculating the averages.

Since POSIX awk contains no sort function, pipe the output of the awk command to the standard Unix sort command.

Please try this:

Script

#!/bin/sh

#first_name,last_name,price_paid,brand,year
#print for each brand, the average price paid

awk -F, '
    NR == 1 {
        next                        # skip header
    }
    {
        price_paid[$4] += $3        # accumulate total price for this brand       
        count[$4] += 1              # increment count of records for this brand
    }
    END {
        for (brand in price_paid) {
            printf "%s,%7.2f\n", brand, price_paid[brand] / count[brand]
        }
    }
' < "${1:?filename required}" | sort

Annotation/Explananation

Invoke the awk command, setting the Field Separator to comma (,) and passing everything between the single quote on this line and the next single quote several lines below, as the script:
```
awk -F, '
```
Skip Header: If the current record number is 1, then skip all processing on the current line (the first line), and get the next line of input:
```
    NR == 1 {
        next                        # skip header
    }
```
Accumulate Price Total Per Brand (this is executed on every line):
The arrays price_paid and count are indexed by the brand string.
Add the current price paid ($3) to the price_paid total for this brand.
Increment the count of records for this brand:
```
    {
        price_paid[$4] += $3        # accumulate total price for this brand    
        count[$4] += 1              # increment count of records for this brand
    }
```
Print the Output Table: After all input is processed, step through the keys (brand) to the price_paid array, and for each brand, print the brand and the average of price_paid for that brand:
```
    END {
        for (brand in price_paid) {
            printf "%s,%7.2f\n", brand, price_paid[brand] / count[brand]
        }
   }
```
Terminate the script argument, redirect input from the filename parameter, and pipe the output of the awk command to the sort command:
```
' < "${1:?filename required}" | sort
```

The single quote (') terminates the script argument to awk.
< "${1:?filename required}" redirects the standard input of awk from the filename specified by the first command line parameter to the script. If there is no parameter, then the shell will print an error message containing "filename required" and exit with error status.