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55 lines
1.7 KiB
Bash
55 lines
1.7 KiB
Bash
1 year ago
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#!/usr/bin/env bash
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# vim:ts=4:sts=4:sw=4:et
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#
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# Author: Hari Sekhon
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# Date: 2023-05-13 00:48:17 +0100 (Sat, 13 May 2023)
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#
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# https://github.com/HariSekhon/DevOps-Bash-tools
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#
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# License: see accompanying Hari Sekhon LICENSE file
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#
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# If you're using my code you're welcome to connect with me on LinkedIn and optionally send me feedback to help steer this or other code I publish
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#
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# https://www.linkedin.com/in/HariSekhon
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#
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set -euo pipefail
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[ -n "${DEBUG:-}" ] && set -x
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srcdir="$(cd "$(dirname "${BASH_SOURCE[0]}")" && pwd)"
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# shellcheck disable=SC1090,SC1091
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. "$srcdir/lib/utils.sh"
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# shellcheck disable=SC2034,SC2154
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usage_description="
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Dumps a trace of the bash profile, .bashrc and all related shell startup costs to a given file
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Useful to find out why spawning new bash shells gets slow
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I've used this to cut down from 20 seconds to 2 seconds
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Tips:
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- bash completion is expensive and to be mostly avoided
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- avoid iterating on directories with lots of files, use a targeted find command to efficiently pre-filter - this also reduces the amount of shell tracing
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eg. for x in somedir_full_of_files/*; do [ -d '\$x' ] || continue; ... ; done <-- this is expensive and noisy in traces
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- running headtail.py -n 5 on the trace file can be useful, although additional timings added to this file reduce the need
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"
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# used by usage() in lib/utils.sh
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# shellcheck disable=SC2034
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usage_args="<filename>"
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help_usage "$@"
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num_args 1 "$@"
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trace_file="$1"
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timestamp "Running bash interactive with shell tracing - output results to '$trace_file'"
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# the 'time' command outputs a separating space line already
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#echo >&2
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time bash -ix -c 'echo' 2>&1 | logger -s 2>"$trace_file"
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echo >&2
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timestamp "Bash profile trace can now be found in the trace file '$trace_file'"
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