Tomato router "can't create =: Read-only file system"

Discussion in 'Tomato Firmware' started by dauntingearth, Mar 21, 2014.

  1. dauntingearth

    dauntingearth Reformed Router Member

    Hi I am trying to set up a script in Tomato router that when it runs it will echo a value dependent on the hour. Script written as follow:
    HOUR=$(date +"%k")
    if [[ $HOUR >= 0 ] && [ $HOUR < 12 ]];then
        echo 'Morning'
        echo 'Evening'
    However when I execute the script, the following returned:
    /tmp/.wxNL0Yv3: line 11: can't create =: Read-only file system
    How to fix it? I am pretty sure I did not ask for an access to any Read-only files
  2. darkknight93

    darkknight93 Networkin' Nut Member

  3. koitsu

    koitsu Network Guru Member

    Your if statement is syntactically incorrect, resulting in the interpreter trying to write data to a file called "=" in whatever the cwd (current working directory) is.

    Secondly, understand that the shell environment under Tomato/TomatoUSB by default is Busybox's shell called ash. It tries to be "bash-like" but has many nuances/differences. There is no manual (thank you Busybox folks *sigh*), so it's recommended you try following the Debian ash manual instead; it's as close as you're gonna get.

    Your code should be changed as follows:

    HOUR=$(($(date +%k)))
    if [[ $HOUR -ge 0 -a $HOUR -lt 12 ]]; then
        echo 'Morning'
        echo 'Evening'
    Things to note:

    1. The HOUR assignment now looks scary, but what it's doing is setting the HOUR variable itself to an actual integer/numeric (vs. a string) using $(( )). Then for the actual value, it uses whatever date +%k returns. Which leads me to...

    2. Your if statement being wrong. > and < for numeric comparisons should be -ge (greater-than-equals) and -lt (less-than). If you were to use > and < on a non-numeric you'd end up doing something very very different than what you expect). Additionally, to add a logical AND, you use -a. All of this is covered in the test man page (or the test section of the above Debian ash page.

    3. I strongly recommend getting in the habit of putting a space after your semicolons, i.e. ]]; then not ]];then. The Busybox ash parser will throw you for a loop (i.e. give you trouble) sometimes.

    Just an FYI: be aware that the % expandos for date on Tomato/TomatoUSB due to use of uClibc, are somewhat different compared to what you might be used to on a "normal" Linux box. The man page for strftime applies "sort of"; some of the expandos are different, and some don't exist at all. Just be aware of this when using date on Tomato/TomatoUSB.

    Finally: for general scripting help, you should really ask folks on the Busybox mailing lists. I understand you're writing a script "on Tomato", but Tomato uses Busybox, and this forum really isn't a "how do I write shell scripts" forum per se. I say that respectfully, no judgement (yes I'm aware of other users having long-standing threads talking about shell scripts here). I just mean to say that the forum here is mainly about Tomato/TomatoUSB as in the firmware, not about Busybox directly.
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