Shell

Shell Scripting

^ OVERVIEW

This local page for Bash shell scripts and notes on shell scripting.

^ Bash Built-in Variables

Some links to useful articles discussing `bash` built-in variables:

• https://avpres.net/Bash/builtin_shell_variables
• https://www.gnu.org/software/bash/manual/html_node/Bash-Variables.html

Bash's built-in variables with short names, as listed in Kernigan and Ritchie's "Unix Programming" book and at the first linked article above:

$0
    The first element passed to the shell is the command name.
$n
    The nth argument passed on the command line. If n ≥ 10, then the syntax must be ${n}.
$*
    All the arguments on the command line. The values are separated by the first character in the shell variable IFS: (${1} … ${n}). See also: the IFS entry in Other Shell Variables.
$@
    All the arguments on the command line. The values are individually quoted: ("${1}" … "${n}").
$#
    The number of command-line arguments.
$?
    The exit value of the last executed command.
$_
    The last argument of the previous command.
$!
    The process ID of the most recent background process.

^ Rename Badly Named Files

How to produce a usable filename which contains <ESC> characters, and to rename that badly named file:

 $ ls -i
 9704871 $'\033\033'   9703029  CMakeLists.txt  10899590  dts          9708845  samples
 $ ls -q `find . -inum 9704871`
 './'$'\033\033'
 $ mv './'$'\033\033' betterfilename

^ Git Diff-tree Helper Script

A helper script for calling `git diff-tree`, which can be used to determine at which project commit one or more files have changed:

#!/bin/bash

CMD_GIT=/usr/bin/git

$CMD_GIT log --oneline | head | cut -d " " -f 1

echo "2024-01-31 git diff-tree helper script in progress . . ."
echo "got $# arguments, arg one single quoted is '$1'"

hashes=`$CMD_GIT log --oneline | head -n ${1} | cut -d " " -f 1`
echo "In $PWD found git commit hashes:"
echo " " $hashes

#i=1
#for hash in $hashes; do echo "("$i")" $hash; (( i++ )); done

#echo "Files changed between commit pairs youngest pairings to oldest:
#for hash in $hashes; do echo "Files changed in git commit:"; git diff-tree -r $hash; echo; done
for hash in $hashes
    do echo "Files changed in git commit:"
    git log -1 --oneline $hash
    git diff-tree -r $hash
    echo
done

echo "done"

exit 0

Script to test compilation of series of git commits:

#!/bin/bash

CMD_GIT=/usr/bin/git

current_branch="NOT_SET"
hashes="NOT_SET"

function usage()
{
    echo "How to use vet-branch.sh:":
    echo
    echo "  $ vet-branches.sh n"
    echo
    echo "Argument 'n' is a number of commits to test in current git branch."
    echo
}

#
# script starting point, akin to int main
#

echo "$0: starting"
if [ $# -lt 1 ]
then
    echo "$0 called with too few arguments!"
    usage
    exit -1
fi

current_branch=`$CMD_GIT branch --show-current`
hashes=`$CMD_GIT log --oneline | head -n $1 | cut -d " " -f 1`

echo "Vetting $1 commits of branch ${current_branch}."
echo "Asked to test commits: $hashes"
echo

date >> branch-commit-vetting-report.txt

for hash in $hashes
    do
    $CMD_GIT checkout --quiet $hash
    echo
    echo "At commit $hash, vetting script in progress"
    echo "---------------------------------------------"
    west build -b rpi_pico -p always
    echo "$hash build result: $?" >> branch-commit-vetting-report.txt
done

echo
echo "Restoring git checkout to starting branch:"
$CMD_GIT checkout $current_branch
echo "$0: done."

exit #?

^ To Research

[ ] Look up `git ls-files` and its options.

[ ] Review `xargs` called with the dash zero option.

Interesting header file from Zephyr RTOS 3.4.0:

`zephyr/include/zephyr/toolchain/xcc_missing_defs.h`