你最喜欢在Bash中处理错误的方法是什么?
我在网上找到的处理错误的最好的例子是William Shotts, Jr在http://www.linuxcommand.org上写的。
他建议在Bash中使用以下函数进行错误处理:
#!/bin/bash
# A slicker error handling routine
# I put a variable in my scripts named PROGNAME which
# holds the name of the program being run. You can get this
# value from the first item on the command line ($0).
# Reference: This was copied from <http://www.linuxcommand.org/wss0150.php>
PROGNAME=$(basename $0)
function error_exit
{
# ----------------------------------------------------------------
# Function for exit due to fatal program error
# Accepts 1 argument:
# string containing descriptive error message
# ----------------------------------------------------------------
echo "${PROGNAME}: ${1:-"Unknown Error"}" 1>&2
exit 1
}
# Example call of the error_exit function. Note the inclusion
# of the LINENO environment variable. It contains the current
# line number.
echo "Example of error with line number and message"
error_exit "$LINENO: An error has occurred."
在Bash脚本中是否有更好的错误处理例程?
另一个需要考虑的问题是返回的退出码。只有“1”是相当标准的，尽管bash本身使用了少数保留的退出码，并且同一页认为用户定义的代码应该在64-113范围内，以符合C/ c++标准。
你也可以考虑使用位向量方法，挂载使用它的退出码:
0 success
1 incorrect invocation or permissions
2 system error (out of memory, cannot fork, no more loop devices)
4 internal mount bug or missing nfs support in mount
8 user interrupt
16 problems writing or locking /etc/mtab
32 mount failure
64 some mount succeeded
OR-ing代码可以让脚本显示多个同时发生的错误。
我更喜欢简单的称呼。所以我用了一些看起来有点复杂，但很容易使用的东西。我通常只是复制并粘贴下面的代码到我的脚本。代码后面有解释。
#This function is used to cleanly exit any script. It does this displaying a
# given error message, and exiting with an error code.
function error_exit {
echo
echo "$@"
exit 1
}
#Trap the killer signals so that we can exit with a good message.
trap "error_exit 'Received signal SIGHUP'" SIGHUP
trap "error_exit 'Received signal SIGINT'" SIGINT
trap "error_exit 'Received signal SIGTERM'" SIGTERM
#Alias the function so that it will print a message with the following format:
#prog-name(@line#): message
#We have to explicitly allow aliases, we do this because they make calling the
#function much easier (see example).
shopt -s expand_aliases
alias die='error_exit "Error ${0}(@`echo $(( $LINENO - 1 ))`):"'
I usually put a call to the cleanup function in side the error_exit function, but this varies from script to script so I left it out. The traps catch the common terminating signals and make sure everything gets cleaned up. The alias is what does the real magic. I like to check everything for failure. So in general I call programs in an "if !" type statement. By subtracting 1 from the line number the alias will tell me where the failure occurred. It is also dead simple to call, and pretty much idiot proof. Below is an example (just replace /bin/false with whatever you are going to call).
#This is an example useage, it will print out
#Error prog-name (@1): Who knew false is false.
if ! /bin/false ; then
die "Who knew false is false."
fi
使用陷阱!
tempfiles=( )
cleanup() {
rm -f "${tempfiles[@]}"
}
trap cleanup 0
error() {
local parent_lineno="$1"
local message="$2"
local code="${3:-1}"
if [[ -n "$message" ]] ; then
echo "Error on or near line ${parent_lineno}: ${message}; exiting with status ${code}"
else
echo "Error on or near line ${parent_lineno}; exiting with status ${code}"
fi
exit "${code}"
}
trap 'error ${LINENO}' ERR
.．.然后，每当你创建一个临时文件:
temp_foo="$(mktemp -t foobar.XXXXXX)"
tempfiles+=( "$temp_foo" )
并且$temp_foo将在退出时被删除，并将打印当前行号。(set -e同样会给你错误退出的行为，尽管它有严重的警告，并削弱了代码的可预测性和可移植性)。
您可以让trap为您调用错误(在这种情况下，它使用默认的退出代码1和无消息)或自己调用它并提供显式值;例如:
error ${LINENO} "the foobar failed" 2
将以状态2退出，并给出一个显式消息。
或者使用-s extdebug，并对陷阱的第一行进行一些修改，以全面地捕获所有非零退出代码(mind set -e非错误非零退出代码):
error() {
local last_exit_status="$?"
local parent_lineno="$1"
local message="${2:-(no message ($last_exit_status))}"
local code="${3:-$last_exit_status}"
# ... continue as above
}
trap 'error ${LINENO}' ERR
shopt -s extdebug
这也与set -eu“兼容”。
这个功能最近对我很有用:
action () {
# Test if the first parameter is non-zero
# and return straight away if so
if test $1 -ne 0
then
return $1
fi
# Discard the control parameter
# and execute the rest
shift 1
"$@"
local status=$?
# Test the exit status of the command run
# and display an error message on failure
if test ${status} -ne 0
then
echo Command \""$@"\" failed >&2
fi
return ${status}
}
可以通过将0或最后一个返回值附加到要运行的命令的名称来调用它，这样就可以连接命令，而不必检查错误值。使用this，这个语句块:
command1 param1 param2 param3...
command2 param1 param2 param3...
command3 param1 param2 param3...
command4 param1 param2 param3...
command5 param1 param2 param3...
command6 param1 param2 param3...
变成这样:
action 0 command1 param1 param2 param3...
action $? command2 param1 param2 param3...
action $? command3 param1 param2 param3...
action $? command4 param1 param2 param3...
action $? command5 param1 param2 param3...
action $? command6 param1 param2 param3...
<<<Error-handling code here>>>
如果任何命令失败，错误代码将被简单地传递到块的末尾。我发现当您不希望在之前的命令失败后执行后续命令，但也不希望脚本立即退出(例如，在循环中)时，它很有用。
阅读这一页上的所有答案启发了我很多。
这是我的提示:
文件内容:lib.trap.sh
lib_name='trap'
lib_version=20121026
stderr_log="/dev/shm/stderr.log"
#
# TO BE SOURCED ONLY ONCE:
#
###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
if test "${g_libs[$lib_name]+_}"; then
return 0
else
if test ${#g_libs[@]} == 0; then
declare -A g_libs
fi
g_libs[$lib_name]=$lib_version
fi
#
# MAIN CODE:
#
###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
set -o pipefail # trace ERR through pipes
set -o errtrace # trace ERR through 'time command' and other functions
set -o nounset ## set -u : exit the script if you try to use an uninitialised variable
set -o errexit ## set -e : exit the script if any statement returns a non-true return value
exec 2>"$stderr_log"
###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
#
# FUNCTION: EXIT_HANDLER
#
###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
function exit_handler ()
{
local error_code="$?"
test $error_code == 0 && return;
#
# LOCAL VARIABLES:
# ------------------------------------------------------------------
#
local i=0
local regex=''
local mem=''
local error_file=''
local error_lineno=''
local error_message='unknown'
local lineno=''
#
# PRINT THE HEADER:
# ------------------------------------------------------------------
#
# Color the output if it's an interactive terminal
test -t 1 && tput bold; tput setf 4 ## red bold
echo -e "\n(!) EXIT HANDLER:\n"
#
# GETTING LAST ERROR OCCURRED:
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
#
# Read last file from the error log
# ------------------------------------------------------------------
#
if test -f "$stderr_log"
then
stderr=$( tail -n 1 "$stderr_log" )
rm "$stderr_log"
fi
#
# Managing the line to extract information:
# ------------------------------------------------------------------
#
if test -n "$stderr"
then
# Exploding stderr on :
mem="$IFS"
local shrunk_stderr=$( echo "$stderr" | sed 's/\: /\:/g' )
IFS=':'
local stderr_parts=( $shrunk_stderr )
IFS="$mem"
# Storing information on the error
error_file="${stderr_parts[0]}"
error_lineno="${stderr_parts[1]}"
error_message=""
for (( i = 3; i <= ${#stderr_parts[@]}; i++ ))
do
error_message="$error_message "${stderr_parts[$i-1]}": "
done
# Removing last ':' (colon character)
error_message="${error_message%:*}"
# Trim
error_message="$( echo "$error_message" | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//' )"
fi
#
# GETTING BACKTRACE:
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
_backtrace=$( backtrace 2 )
#
# MANAGING THE OUTPUT:
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
local lineno=""
regex='^([a-z]{1,}) ([0-9]{1,})$'
if [[ $error_lineno =~ $regex ]]
# The error line was found on the log
# (e.g. type 'ff' without quotes wherever)
# --------------------------------------------------------------
then
local row="${BASH_REMATCH[1]}"
lineno="${BASH_REMATCH[2]}"
echo -e "FILE:\t\t${error_file}"
echo -e "${row^^}:\t\t${lineno}\n"
echo -e "ERROR CODE:\t${error_code}"
test -t 1 && tput setf 6 ## white yellow
echo -e "ERROR MESSAGE:\n$error_message"
else
regex="^${error_file}\$|^${error_file}\s+|\s+${error_file}\s+|\s+${error_file}\$"
if [[ "$_backtrace" =~ $regex ]]
# The file was found on the log but not the error line
# (could not reproduce this case so far)
# ------------------------------------------------------
then
echo -e "FILE:\t\t$error_file"
echo -e "ROW:\t\tunknown\n"
echo -e "ERROR CODE:\t${error_code}"
test -t 1 && tput setf 6 ## white yellow
echo -e "ERROR MESSAGE:\n${stderr}"
# Neither the error line nor the error file was found on the log
# (e.g. type 'cp ffd fdf' without quotes wherever)
# ------------------------------------------------------
else
#
# The error file is the first on backtrace list:
# Exploding backtrace on newlines
mem=$IFS
IFS='
'
#
# Substring: I keep only the carriage return
# (others needed only for tabbing purpose)
IFS=${IFS:0:1}
local lines=( $_backtrace )
IFS=$mem
error_file=""
if test -n "${lines[1]}"
then
array=( ${lines[1]} )
for (( i=2; i<${#array[@]}; i++ ))
do
error_file="$error_file ${array[$i]}"
done
# Trim
error_file="$( echo "$error_file" | sed -e 's/^[ \t]*//' | sed -e 's/[ \t]*$//' )"
fi
echo -e "FILE:\t\t$error_file"
echo -e "ROW:\t\tunknown\n"
echo -e "ERROR CODE:\t${error_code}"
test -t 1 && tput setf 6 ## white yellow
if test -n "${stderr}"
then
echo -e "ERROR MESSAGE:\n${stderr}"
else
echo -e "ERROR MESSAGE:\n${error_message}"
fi
fi
fi
#
# PRINTING THE BACKTRACE:
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
test -t 1 && tput setf 7 ## white bold
echo -e "\n$_backtrace\n"
#
# EXITING:
# ~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~ #
test -t 1 && tput setf 4 ## red bold
echo "Exiting!"
test -t 1 && tput sgr0 # Reset terminal
exit "$error_code"
}
trap exit_handler EXIT # ! ! ! TRAP EXIT ! ! !
trap exit ERR # ! ! ! TRAP ERR ! ! !
###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
#
# FUNCTION: BACKTRACE
#
###~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~~##
function backtrace
{
local _start_from_=0
local params=( "$@" )
if (( "${#params[@]}" >= "1" ))
then
_start_from_="$1"
fi
local i=0
local first=false
while caller $i > /dev/null
do
if test -n "$_start_from_" && (( "$i" + 1 >= "$_start_from_" ))
then
if test "$first" == false
then
echo "BACKTRACE IS:"
first=true
fi
caller $i
fi
let "i=i+1"
done
}
return 0
用法示例:
文件内容:trap-test.sh
#!/bin/bash
source 'lib.trap.sh'
echo "doing something wrong now .."
echo "$foo"
exit 0
运行:
bash trap-test.sh
输出:
doing something wrong now ..
(!) EXIT HANDLER:
FILE: trap-test.sh
LINE: 6
ERROR CODE: 1
ERROR MESSAGE:
foo: unassigned variable
BACKTRACE IS:
1 main trap-test.sh
Exiting!
从下面的屏幕截图可以看到，输出是彩色的，错误消息是使用的语言。
