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author | Tom Ryder <tom@sanctum.geek.nz> | 2017-04-05 20:06:39 +1200 |
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committer | Tom Ryder <tom@sanctum.geek.nz> | 2017-04-05 20:46:47 +1200 |
commit | c8ab406749124d2e762ad5cf53963070113afd0f (patch) | |
tree | 54c9721a06957ebe7098a211eea803b0230c0f5d /bin/chc.sh | |
parent | Handle POSIX correctness in ~/.bash_profile (diff) | |
download | dotfiles-c8ab406749124d2e762ad5cf53963070113afd0f.tar.gz dotfiles-c8ab406749124d2e762ad5cf53963070113afd0f.zip |
Apply runtime shebanging to POSIX shell
Diffstat (limited to 'bin/chc.sh')
-rw-r--r-- | bin/chc.sh | 30 |
1 files changed, 30 insertions, 0 deletions
diff --git a/bin/chc.sh b/bin/chc.sh new file mode 100644 index 00000000..8b15317c --- /dev/null +++ b/bin/chc.sh @@ -0,0 +1,30 @@ +# Cache the output of a command and emit it straight from the cache if not +# expired on each run + +# First argument is the cache path, second is the duration in seconds +cac=$1 dur=$2 +shift 2 + +# Get the current timestamp with uts(1df) +uts=$(uts) || exit + +# Function checks cache exists, is readable, and not expired +fresh() { + [ -f "$cac" ] || return + [ -r "$cac" ] || return + exp=$(sed 1q -- "$cac") || return + [ "$((exp > uts))" -eq 1 ] +} + +# Write runs the command and writes it to the cache +write() { + exp=$((uts + dur)) + printf '%u\n' "$exp" + "$@" +} + +# If the cache isn't fresh, try to write a new one, or bail out +fresh "$cac" || write "$@" > "$cac" || exit + +# Emit the content (exclude the first line, which is the timestamp) +sed 1d -- "$cac" |