Author Archives: henry

How to download Xcode simulator directly

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Due to network issues, downloading the runtime is not always smooth, so it is best to download it directly with support for resuming interrupted downloads.

1. Find the downloaded URL

Use console

  1. Open Xcode, open preferences, go to the Components section.
  2. Open the Console App, clear the console.
  3. Go back to the Xcode preferences. Start the simulator download, then cancel it.
  4. Now in the Console, you will see something about the cancellation with the download URL. ( Process is xcode and maybe search keyword download )
  5. Copy the URL from the Console. Then download it by safari. ( or some other way which is authed )

Offical dowloaded from apple

  1. Go to apple developer website and login.
  2. You can find all Xcode dmg/xip files directly on https://developer.apple.com/download/all/ (requires Apple ID).
  3. Find the simulator runtimes you want and download.

2. Download the DMG file

Now you can download it using Safari or another authorized method.

3. Add runtime

Finally, just run

xcrun simctl runtime add iOS_xxx_Simulator_Runtime.dmg

Write commands with multiple lines in Dockerfile

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There are several ways to write commands with multiple lines in Dockerfile, for example you wanna echo a bash file entrypoint.sh with content:

#!/bin/bash
echo 3
echo 2
echo 1
echo run

You could:

Using printf

RUN printf '#!/bin/bash\necho 3\necho 2\necho 1\necho run' > /entrypoint.sh

Using cat

RUN sh -c "$(/bin/echo -e "cat > /entrypoint.sh <<EOF\
\n#!/bin/bash\
\necho 3\
\necho 2\
\necho 1\
\necho run\
\nEOF\n")"

Using echo -e

RUN echo -e " #!/bin/bash\n\
echo 3\n\
echo 2\n\
echo 1\n\
echo run" > /entrypoint.sh

Using $'...'

The $’…’ feature is known as "ANSI-C quoting" but it’s not a POSIX shell > feature. According to unix.stackexchange.com/a/371873/109111 it was > originally a ksh93 feature but it is now available in bash, zsh, mksh, > FreeBSD sh and in busybox’s ash

RUN echo $'#!/bin/bash\n\
echo 3\n\
echo 2\n\
echo 1\n\
echo run' > /entrypoint.sh

echo -e & $'...' are both similar in that they support the following escape sequences:

\a     alert (bell)
\b     backspace
\e
\E     an escape character
\f     form feed
\n     new line
\r     carriage return
\t     horizontal tab
\v     vertical tab
\\     backslash
\0nnn  the eight-bit character whose value is the octal value nnn (zero to three octal digits)
\xHH   the eight-bit character whose value is the hexadecimal value HH (one or two hex digits)
\uHHHH the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHH (one to four hex digits)
\UHHHHHHHH
     the Unicode (ISO/IEC 10646) character whose value is the hexadecimal value HHHHHHHH (one to eight hex digits)

They do have differences. In addition to the above, echo -e supports:

\c     suppress further output
\0nnn  the eight-bit character whose value is the octal value nnn (zero to three octal digits)

By contrast, $'....' supports:

 \'     single quote
 \"     double quote
 \nnn   the eight-bit character whose value is the octal value nnn (one to three digits)
 \cx    a control-x character

How to bash multithread?

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I do think using xargs to run code multithread in bash is a better way, you still could use fifo. Just like the sample below: 

#!/bin/bash
function a_sub
{
    sleep 3
}
tmp_fifofile="/tmp/$$.fifo"
mkfifo $tmp_fifofile
exec 6<>$tmp_fifofile

rm $tmp_fifofile

thread=15

for((i=0;i<$thread;i++));do
    echo
done >&6

for((i=0;i<50;i++));do
    read -u 6
    {
        a_sub && {
            echo "a_sub is finished"
        } || {
            echo "sub error"
        }
        echo >&6
    }&
done

exec 6>&-

wait

Useful bash functions

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Get bash file absolute path

realpath(){
  path="$1"
  while [ -h "$path" ] ; do path="$(readlink "$path")"; done
  echo "$(cd "$(dirname "$path")"; echo -n "$(pwd)/$(basename "$path")")";
}

Log

log() {
  if [[ -n "$VERBOSE" ]]; then echo -e "$@"; else test 1; fi
}

error() {
  echo "$@" >&2
  exit 1
}
warning() {
  echo "$@" >&2
}

function check_status {
  if [ $? -ne 0 ];then
    error ${@:-"Encountered an error, aborting!"}
  fi
}

Loop find

find . -type f -iname "*.txt" -print0 | while IFS= read -r -d $'\0' line; do
  echo "$line"
  ls -l "$line"
done

Removing alpha channel of pngs using Imagemagick

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Apple has released new version of iTunes Connect and you would get an error message when try to send images on iTunes Connect for apps.

It would tell you that “Invalid Icon” balabala “xxx.png with an alpha channel. Icons should not have an alpha channel.” and so on.

You can check your pngs to see whether it has an alpha channel.

find . -type f -name "*.png" -exec identify -format '"%d/%f" %[channels]\n' {} \;

And you can remove their alpha channel to make apple happier.

find . -type f -name "*.png" -exec mogrify -background white -alpha off -flatten {} \;

You’d better run it in the specific directory so that you can limit the affect.

That’s all.