完全通过FIFO连接到MySQL客户端

在Bash脚本中，我希望保持MySQL会话在多个连续访问中打开；访问MySQL的常用方法是为每个SQL命令或一组命令打开一个单独的会话，例如

mysql -u user -e "show tables;"

该方法的局限性在于，对于需要双重的事务，会丢失原子性和锁定状态：例如，在以下双重操作的整个过程中，不可能在表T上保留锁定状态：

### Minimalistic example
data=$(mysql -e "\
    lock table T write;
    select col from T;
")
# ...
# parse 'data' and compute 'output' variable
# ...
mysql -e "insert into T values ($output);"

我的解决方案是通过使用两个FIFO保持MySQL会话在多个访问中的开放性，并在后台挂起进程

提议的解决办法： 创建一对FIFO:mkfifo IN OUT。 将MySQL客户端实例和一个虚拟实例设置到位，同时保持管道打开并防止SIGPIPE信号：

---

这是预期的行为吗？另外，我想知道是否有可能在没有自定义homebrews的情况下在Bash中运行双重操作。

下面是一个简单的示例，再现了您描述的锁定行为：

while :; do sleep 1; done <IN >OUT

sed s/^/::/ >IN <OUT

cat IN

echo x > OUT

---

通过FIFO的控制流比等待文件在while循环中显示更有吸引力；但是FIFO出人意料地难以正确使用。

FIFO的问题是，当输入数据的每个进程终止时，它会向正在读取数据的进程发出信号（在本例中为mysql），表示数据结束，因此终止

诀窍是确保有一个过程使FIFO输入始终处于活动状态。您可以通过在后台运行sleep 9999999>fiofile来实现这一点

例如：

#!/bin/sh

mkfifo /tmp/sqlpipe

sleep 2147483647 > /tmp/sqlpipe &
PID=$!

mysql -B -uUSER -pPASSWORD < /tmp/sqlpipe &

# all set up, now just push the SQL queries to the pipe, exemple:
echo "INSERT INTO table VALUES (...);" > /tmp/sqlpipe
echo "INSERT INTO table VALUES (...);" > /tmp/sqlpipe
echo "INSERT INTO table VALUES (...);" > /tmp/sqlpipe
cat "mysqldump.sql" > /tmp/sqlpipe
echo "DELETE FROM table WHERE ...;" > /tmp/sqlpipe

# done! terminate pipe
kill -s SIGINT $PID
rm /tmp/sqlpipe

querygenerator.sh：

---

不久前，我使用unix socketpair开发了一个针对此类问题的作弊工具。它只会在脚本在后台运行时保持，但处理FIFO要容易得多

socketpair调用在指定的域中创建一对未命名的连接套接字，该套接字为指定类型，并使用可选的指定协议

下面是一个完整的示例，包含二进制文件的源代码。不要气馁，你可以在一个交互式shell中轻松地玩转这个想法：

local:/# ./socketpair /bin/bash
$ cat <& $DUP1 | tr '[:lower:]' '[:upper:]' &
$ echo 'Hello SocketPair!' >& $DUP2
HELLO SOCKETPAIR!
$

我将源代码包含在脚本中，以防我将脚本移动到某个地方，但找不到二进制文件：

## Source code for simple 'socketpair' binary
## Compile with "cc -o socketpair socketpair.c"
: <<'SOURCE'
--[ cut here ]--
/** 
* @file socketpair.c
* @author christopher anserson
* @date 2012-04-28
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>

char* custom_itoa(int i) {
    static char output[24];
     return sprintf(output, "%d", i), output;
}

int main(int argc, char **argv) {
    int sv[2]; /* the pair of socket descriptors */

    if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == -1) {
        perror("socketpair");
        exit(1);
    }
     setenv("DUP1", custom_itoa(sv[0]), 1);
     setenv("DUP2", custom_itoa(sv[1]), 1);

     /* now exec whatever script needed these paired sockets */
     execv(argv[1], &argv[1]);
    return 0;
}
--[cut here]--
SOURCE

---

我知道这个线程很旧，但我也在寻找一个舒适的bash-mysql会话实现，并没有找到足够好的东西来满足我的需要，所以我写了我自己的一个，我想与全世界分享

############### BASIC MYSQL SESSION IMPLEMENTATION FOR BASH (by Norman 

Geist 2015) #############
# requires coproc, stdbuf, mysql
#args: handle query
function mysql_check {
  local handle
  handle=(${1//_/ })
  #has right structure && is still running && we opened it?
  if [[ ${#handle[*]} == 3 ]] && ps -p ${handle[2]} 2>> /dev/null >> /dev/null && { echo "" >&${handle[1]}; } 2> /dev/null; then
    return 0
  fi
  return 1
}

# open mysql connection
#args: -u user [-H host] [-p passwd] -d db
#returns $HANDLE
function mysql_connect {
  local argv argc user pass host db HANDLEID i
  #prepare args
  argv=($*)
  argc=${#argv[*]}

  #get options
  user=""
  pass=""
  host="localhost"
  db=""
  for ((i=0; $i < $argc; i++))
  do
    if [[ ${argv[$i]} == "-h" ]]; then
      echo "Usage: -u user [-H host] [-p passwd] -d db"
      return 0
    elif [[ ${argv[$i]} == "-u" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    user=${argv[$i]}
      else
    echo "ERROR: -u expects argument!"
    return 1
      fi
    elif [[ ${argv[$i]} == "-p" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    pass="-p"${argv[$i]}
      else
    echo "ERROR: -p expects argument!"
    return 1
      fi
    elif [[ ${argv[$i]} == "-H" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    host=${argv[$i]}
      else
    echo "ERROR: -H expects argument!"
    return 1
      fi
    elif [[ ${argv[$i]} == "-d" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    db=${argv[$i]}
      else
    echo "ERROR: -d expects argument!"
    return 1
      fi
    fi
  done

  if [[ ${#user} -lt 1 || ${#db} -lt 1 ]]; then
    echo "ERROR: Options -u user and -d db are required!"
    return 1;
  fi

  #init connection and channels
  #we do it in XML cause otherwise we can't detect the end of data and so would need a read timeout O_o
  HANDLEID="MYSQL$RANDOM"
  eval "coproc $HANDLEID { stdbuf -oL mysql -u $user $pass -h $host -D $db --force --unbuffered --xml -vvv 2>&1; }" 2> /dev/null
  HANDLE=$(eval 'echo ${'${HANDLEID}'[0]}_${'${HANDLEID}'[1]}_${'${HANDLEID}'_PID}')
  if mysql_check $HANDLE; then
    export HANDLE
    return 0
  else
    echo "ERROR: Connection failed to $user@$host->DB:$db!"
    return 1
  fi
}

#args: handle query
#return: $DATA[0] = affected rows/number of sets; 
#        $DATA[1] = key=>values pairs following
#        $DATA[2]key; DATA[3]=val ...
function mysql_query {
  local handle query affected line results_open row_open cols key val 
  if ! mysql_check $1; then
    echo "ERROR: Connection not open!"
    return 1
  fi
  handle=(${1//_/ })

  #delimit query; otherwise we block forever/timeout
  query=$2
  if [[ ! "$query" =~ \;\$ ]]; then
    query="$query;"
  fi
  #send query
  echo "$query" >&${handle[1]}

  #get output
  DATA=();
  DATA[0]=0
  DATA[1]=0
  results_open=0
  row_open=0
  cols=0
  while read -t $MYSQL_READ_TIMEOUT -ru ${handle[0]} line
  do 
    #WAS ERROR?
    if [[ "$line" == *"ERROR"* ]]; then
      echo "$line"
      return 1
    #WAS INSERT/UPDATE?
    elif [[ "$line" == *"Query OK"* ]]; then
      affected=$([[ "$line" =~ Query\ OK\,\ ([0-9]+)\ rows?\ affected ]] && echo ${BASH_REMATCH[1]})
      DATA[0]=$affected
      export DATA
      return 0
    fi

    #BEGIN OF RESULTS
    if [[ $line =~ \<resultset ]]; then
      results_open=1
    fi

    #RESULTS
    if [[ $results_open == 1 ]]; then
      if [[ $line =~ \<row ]]; then
    row_open=1
    cols=0
      elif [[ $line =~ \<field && $row_open == 1 ]]; then
    key=$([[ "$line" =~ name\=\"([^\"]+)\" ]] && echo ${BASH_REMATCH[1]})
    val=$([[ "$line" =~ \>(.*)\<\/ ]] && echo ${BASH_REMATCH[1]} || echo "NULL")
    DATA[${#DATA[*]}]=$key
    DATA[${#DATA[*]}]=$val
    cols=$[$cols+1]
      elif [[ $line =~ \<\/row ]]; then
    row_open=0
    DATA[0]=$[${DATA[0]}+1]
    DATA[1]=$cols
      fi
    fi

    #END OF RESULTS
    if [[ $line =~ \<\/resultset ]]; then
      export DATA
      return 0
    fi
  done
  #we can only get here
  #if read times out O_o
  echo "$FUNCNAME: Read timed out!"
  return 1
}

#args: handle
function mysql_close {
  local handle
  if ! mysql_check $1; then
    echo "ERROR: Connection not open!"
    return 1
  fi
  handle=(${1//_/ })
  echo "exit;" >&${handle[1]}

  if ! mysql_check $1; then
    return 0
  else
    echo "ERROR: Couldn't close connection!"
    return 1
  fi
}
############### END BASIC MYSQL SESSION IMPLEMENTATION FOR BASH ################################

# Example usage
#define timeout for read command, in case of server error etc.
export MYSQL_READ_TIMEOUT=10

# Connect to db and get $HANDLE
mysql_connect -u mydbuser -d mydb -H mydbserver

#query db and get $DATA
mysql_query $HANDLE "SELECT dt_whatever from tbl_lol WHERE dt_rofl=10"

#close connection
mysql_close $HANDLE

通常，所有查询都应该工作，甚至选择count* 示例如何循环两列查询的返回数据 例如，从…中选择dt_id、dt_名称。。。

---

您是否尝试改用附加重定向>>或管道？好问题，祝你好运！如果您没有被迫使用shell脚本，并且安装了PHP，那么为什么不创建一个包装shell来创建到已建立连接的管道命令呢。您可以从这里开始：我对一些bash脚本也有同样的问题。在某一点上，它变得非常不容易管理。然后我发现了Python，它成为了我选择的语言。它有一个与MySQL接口的模块。

#!/bin/sh

mkfifo /tmp/sqlpipe

sleep 2147483647 > /tmp/sqlpipe &
PID=$!

mysql -B -uUSER -pPASSWORD < /tmp/sqlpipe &

# all set up, now just push the SQL queries to the pipe, exemple:
echo "INSERT INTO table VALUES (...);" > /tmp/sqlpipe
echo "INSERT INTO table VALUES (...);" > /tmp/sqlpipe
echo "INSERT INTO table VALUES (...);" > /tmp/sqlpipe
cat "mysqldump.sql" > /tmp/sqlpipe
echo "DELETE FROM table WHERE ...;" > /tmp/sqlpipe

# done! terminate pipe
kill -s SIGINT $PID
rm /tmp/sqlpipe

#!/bin/sh
./querygenerator.sh | mysql -B -uUSER -pPASSWORD

#!/bin/sh
echo "INSERT INTO table VALUES (...);"
echo "INSERT INTO table VALUES (...);"
echo "INSERT INTO table VALUES (...);"
cat "mysqldump.sql"
echo "DELETE FROM table WHERE ...;"

local:/# ./socketpair /bin/bash
$ cat <& $DUP1 | tr '[:lower:]' '[:upper:]' &
$ echo 'Hello SocketPair!' >& $DUP2
HELLO SOCKETPAIR!
$

#!./socketpair /usr/bin/env bash
# We are now in a BASH script with a pair of linked sockets,
# $DUP1 and $DUP2

## Background job ## Received data on DUP1
(
    while read -r -u $DUP1
    do
        echo "Received: $REPLY"
    done 
) &


## Foreground task ## Sends data to DUP2
counter=0
while true
do
    echo Test $(( counter++ )) >&$DUP2
    sleep 1
done

## Source code for simple 'socketpair' binary
## Compile with "cc -o socketpair socketpair.c"
: <<'SOURCE'
--[ cut here ]--
/** 
* @file socketpair.c
* @author christopher anserson
* @date 2012-04-28
*/
#include <stdio.h>
#include <stdlib.h>
#include <errno.h>
#include <sys/socket.h>

char* custom_itoa(int i) {
    static char output[24];
     return sprintf(output, "%d", i), output;
}

int main(int argc, char **argv) {
    int sv[2]; /* the pair of socket descriptors */

    if (socketpair(AF_UNIX, SOCK_STREAM, 0, sv) == -1) {
        perror("socketpair");
        exit(1);
    }
     setenv("DUP1", custom_itoa(sv[0]), 1);
     setenv("DUP2", custom_itoa(sv[1]), 1);

     /* now exec whatever script needed these paired sockets */
     execv(argv[1], &argv[1]);
    return 0;
}
--[cut here]--
SOURCE

############### BASIC MYSQL SESSION IMPLEMENTATION FOR BASH (by Norman 

Geist 2015) #############
# requires coproc, stdbuf, mysql
#args: handle query
function mysql_check {
  local handle
  handle=(${1//_/ })
  #has right structure && is still running && we opened it?
  if [[ ${#handle[*]} == 3 ]] && ps -p ${handle[2]} 2>> /dev/null >> /dev/null && { echo "" >&${handle[1]}; } 2> /dev/null; then
    return 0
  fi
  return 1
}

# open mysql connection
#args: -u user [-H host] [-p passwd] -d db
#returns $HANDLE
function mysql_connect {
  local argv argc user pass host db HANDLEID i
  #prepare args
  argv=($*)
  argc=${#argv[*]}

  #get options
  user=""
  pass=""
  host="localhost"
  db=""
  for ((i=0; $i < $argc; i++))
  do
    if [[ ${argv[$i]} == "-h" ]]; then
      echo "Usage: -u user [-H host] [-p passwd] -d db"
      return 0
    elif [[ ${argv[$i]} == "-u" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    user=${argv[$i]}
      else
    echo "ERROR: -u expects argument!"
    return 1
      fi
    elif [[ ${argv[$i]} == "-p" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    pass="-p"${argv[$i]}
      else
    echo "ERROR: -p expects argument!"
    return 1
      fi
    elif [[ ${argv[$i]} == "-H" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    host=${argv[$i]}
      else
    echo "ERROR: -H expects argument!"
    return 1
      fi
    elif [[ ${argv[$i]} == "-d" ]]; then
      i=$[$i+1]
      if [[ ${#argv[$i]} -gt 0 ]]; then
    db=${argv[$i]}
      else
    echo "ERROR: -d expects argument!"
    return 1
      fi
    fi
  done

  if [[ ${#user} -lt 1 || ${#db} -lt 1 ]]; then
    echo "ERROR: Options -u user and -d db are required!"
    return 1;
  fi

  #init connection and channels
  #we do it in XML cause otherwise we can't detect the end of data and so would need a read timeout O_o
  HANDLEID="MYSQL$RANDOM"
  eval "coproc $HANDLEID { stdbuf -oL mysql -u $user $pass -h $host -D $db --force --unbuffered --xml -vvv 2>&1; }" 2> /dev/null
  HANDLE=$(eval 'echo ${'${HANDLEID}'[0]}_${'${HANDLEID}'[1]}_${'${HANDLEID}'_PID}')
  if mysql_check $HANDLE; then
    export HANDLE
    return 0
  else
    echo "ERROR: Connection failed to $user@$host->DB:$db!"
    return 1
  fi
}

#args: handle query
#return: $DATA[0] = affected rows/number of sets; 
#        $DATA[1] = key=>values pairs following
#        $DATA[2]key; DATA[3]=val ...
function mysql_query {
  local handle query affected line results_open row_open cols key val 
  if ! mysql_check $1; then
    echo "ERROR: Connection not open!"
    return 1
  fi
  handle=(${1//_/ })

  #delimit query; otherwise we block forever/timeout
  query=$2
  if [[ ! "$query" =~ \;\$ ]]; then
    query="$query;"
  fi
  #send query
  echo "$query" >&${handle[1]}

  #get output
  DATA=();
  DATA[0]=0
  DATA[1]=0
  results_open=0
  row_open=0
  cols=0
  while read -t $MYSQL_READ_TIMEOUT -ru ${handle[0]} line
  do 
    #WAS ERROR?
    if [[ "$line" == *"ERROR"* ]]; then
      echo "$line"
      return 1
    #WAS INSERT/UPDATE?
    elif [[ "$line" == *"Query OK"* ]]; then
      affected=$([[ "$line" =~ Query\ OK\,\ ([0-9]+)\ rows?\ affected ]] && echo ${BASH_REMATCH[1]})
      DATA[0]=$affected
      export DATA
      return 0
    fi

    #BEGIN OF RESULTS
    if [[ $line =~ \<resultset ]]; then
      results_open=1
    fi

    #RESULTS
    if [[ $results_open == 1 ]]; then
      if [[ $line =~ \<row ]]; then
    row_open=1
    cols=0
      elif [[ $line =~ \<field && $row_open == 1 ]]; then
    key=$([[ "$line" =~ name\=\"([^\"]+)\" ]] && echo ${BASH_REMATCH[1]})
    val=$([[ "$line" =~ \>(.*)\<\/ ]] && echo ${BASH_REMATCH[1]} || echo "NULL")
    DATA[${#DATA[*]}]=$key
    DATA[${#DATA[*]}]=$val
    cols=$[$cols+1]
      elif [[ $line =~ \<\/row ]]; then
    row_open=0
    DATA[0]=$[${DATA[0]}+1]
    DATA[1]=$cols
      fi
    fi

    #END OF RESULTS
    if [[ $line =~ \<\/resultset ]]; then
      export DATA
      return 0
    fi
  done
  #we can only get here
  #if read times out O_o
  echo "$FUNCNAME: Read timed out!"
  return 1
}

#args: handle
function mysql_close {
  local handle
  if ! mysql_check $1; then
    echo "ERROR: Connection not open!"
    return 1
  fi
  handle=(${1//_/ })
  echo "exit;" >&${handle[1]}

  if ! mysql_check $1; then
    return 0
  else
    echo "ERROR: Couldn't close connection!"
    return 1
  fi
}
############### END BASIC MYSQL SESSION IMPLEMENTATION FOR BASH ################################

# Example usage
#define timeout for read command, in case of server error etc.
export MYSQL_READ_TIMEOUT=10

# Connect to db and get $HANDLE
mysql_connect -u mydbuser -d mydb -H mydbserver

#query db and get $DATA
mysql_query $HANDLE "SELECT dt_whatever from tbl_lol WHERE dt_rofl=10"

#close connection
mysql_close $HANDLE

$DATA[0] = affected rows/number of sets;
$DATA[1] = number of key=>values pairs following;
$DATA[2] = key1;
$DATA[3] = value1;
      [...]
$DATA[n-1] = keyn;
$DATA[n]   = valuen;

fields=2
for ((i=2; $i<$((${DATA[0]}*${DATA[1]}*$fields)); i+=$((${DATA[1]}*$fields))))
do
    field1key   = ${DATA[$i]};   #this is "dt_id"
    field1value = ${DATA[$i+1]}; #this is the value for dt_id
    field2key   = ${DATA[$i+2]}; #this is "dt_name"
    field2value = ${DATA[$i+3]}; #this is the value  for dt_name
done