-c选项为一次发送的请求数量，及并发量。-n选项为请求次数。

案例如下：

ab  -n 4 -c 6   http://office.xxxx.com报错，因为并发量(6)大于请求总数(4)

ab  -n 3 -c 2   http://office.xxxx.com 请求网址3次

ab -n 4 -c 2 http://office.xxxx.com 请求网址4次

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Usage: ab [options] [http[s]://]hostname[:port]/path Options are:

-n requests     Number of requests to perform

-c concurrency  Number of multiple requests to make

-t timelimit    Seconds to max. wait for responses

-b windowsize   Size of TCP send/receive buffer, in bytes

-p postfile     File containing data to POST. Remember also to set -T

-u putfile      File containing data to PUT. Remember also to set -T

-T content-type Content-type header for POSTing, eg.

'application/x-www-form-urlencoded'

Default is 'text/plain'

-v verbosity    How much troubleshooting info to print

-w              Print out results in HTML tables

-i              Use HEAD instead of GET

-x attributes   String to insert as table attributes

-y attributes   String to insert as tr attributes

-z attributes   String to insert as td or th attributes

-C attribute    Add cookie, eg. 'Apache=1234. (repeatable)

-H attribute    Add Arbitrary header line, eg. 'Accept-Encoding: gzip'

Inserted after all normal header lines. (repeatable)

-A attribute    Add Basic WWW Authentication, the attributes

are a colon separated username and password.

-P attribute    Add Basic Proxy Authentication, the attributes

are a colon separated username and password.

-X proxy:port   Proxyserver and port number to use

-V              Print version number and exit

-k              Use HTTP KeepAlive feature

-d              Do not show percentiles served table.

-S              Do not show confidence estimators and warnings.

-g filename     Output collected data to gnuplot format file.

-e filename     Output CSV file with percentages served

-r              Don't exit on socket receive errors.

-h              Display usage information (this message)

-Z ciphersuite  Specify SSL/TLS cipher suite (See openssl ciphers)

-f protocol     Specify SSL/TLS protocol (SSL2, SSL3, TLS1, or ALL)