1 #!/bin/bash
- 2 #=============================================================================== 3 # 4 # FILE:
condition_expression_test.sh 5 # 6 #
USAGE: ./condition_expression_test.sh 7 # 8 #
DESCRIPTION: 9 # 10 #
OPTIONS: --- 11 # REQUIREMENTS:
--- 12 # BUGS:
--- 13 #
NOTES: --- 14 # AUTHOR:
daojoo, daojoo@qq.com 15 # ORGANIZATION:
lit 16 #
CREATED: 2012年03月10日 22时55分23秒 CST 17 # REVISION: --- 18 #=============================================================================== 19 20 set-o nounset# Treat unset variables as an
error 21 22 #以下内容来源于bash的man手册 [man
bash] 23 24 #CONDITIONAL
EXPRESSIONS 25 #Conditional
expressions are used by the [[ compound 26 #command and the test and [ builtin
commands to test file attributes and perform 27 #string and arithmetic comparisons.
Expressions are formed from the following 28 #unary or binary primaries. If any file
argument to one of the primaries is of 29 #the form /dev/fd/n, then file descriptor n
is checked. If the file argument to 30 #one of the primaries is one of /dev/stdin,
/dev/stdout, or /dev/stderr, file 31 #descriptor 0, 1, or 2, respectively, is
checked. 32 #条件表达式 33 #1.用于何处？ 34 #
用于[[组合命令中 35 #
用于test和[这两个内建命令中 36 #2.用来干什么？ 37 #
测试文件属性 38 #
字符串和算术比较 39 #3.如何构建？ 40 #
由参数、unary primaries、binary primaries构建 41 # 42 #Unless otherwise specified, primaries that
operate on files follow symbolic 43 #links and operate on the target of the
link, rather than the link itself. 44 #如果primaries后面的参数是一个符号链接，除非另行指明，否则运算符将作用于目标文件， 45 #而非链接本身 46 # 47 #When
used with [[, The < and > operators sort lexicographically using
the 48 #current
locale. 49 #当使用[[p这个组合命令时，<
和 > 这两个二元操作符会使用当前locale将它的两个按字典排序 50 # 51 #See the description of the test builtin
command (section SHELL BUILTIN COMMANDS 52 #below) for the handling of parameters
(i.e. missing parameters). 53 54 #以下是primaries及测试 55 56 #-a file 57 # True if file
exists. 58 # [all
只要文件存在]文件存在时为true 59 #-e
file 60 # True
if file exists. 61 # [exist
存在]作用同-a，存在即为true 62 touchtest.txt; 63 if [-a test.txt ];then 64 echo"test.txt
exists."; 65 fi 66 rm-ftest.txt; 67 if [!-a test.txt ];then 68 echo"test.txt
not exists."; 69 fi 70 #output: 71 #test.txt
exists. 72 #test.txt
not exists. 73 74 #-b file 75 # True if file
exists and is a block special file. 76 # [block
块]文件存在且是块文件时为true 77 BLOCK_FILE=/dev/sda; 78 if [-b$BLOCK_FILE];then 79 echo"$BLOCK_FILE is a block file."; 80 fi 81 unset BLOCK_FILE; 82 #output: 83 #/dev/sda is a block file. 84 85 #-c file 86 # True if file
exists and is a character special file. 87 # [character
字符]存在且是字符文件时为true 88 89 90 #-d
file 91 # True
if file exists and is a directory. 92 # [directory
目录]存在且是目录时为true 93 DIR=/ 94 if [-d$DIR];then 95 echo"$DIR is a directory."; 96 fi 97 unset DIR; 98 #output: 99 #/ is a directory. 100 101 #-f
file 102 # True
if file exists and is a regular file. 103 # [file
普通文件]存在且是普通文件时为true 104 REGULAR_FILE=/etc/profile
; 105 NONREGULAR_FILE=/dev/sda
; 106 if [-f$REGULAR_FILE];then 107 echo"$REGULAR_FILE is a regular file."; 108 else 109 echo"$REGULAR_FILE is not a regular file."; 110 fi 111 if [-f$NONREGULAR_FILE];then 112 echo"$NONREGULAR_FILE is a regular file."; 113 else 114 echo"$NONREGULAR_FILE is not a regular file."; 115 fi 116 unset REGULAR_FILE ; 117 unset NONREGULAR_FILE ; 118 #output: 119 #/etc/profile
is a regular file. 120 #/dev/sda
is not a regular file. 121 122 #-g file 123 # True if file
exists and is set-group-id. 124 # [setgid]存在且文件属性为"......s..."时为true，其中.代表-,r,w,x中的任意一个 125 touch setgid.txt
; 126 chmod6755 setgid.txt ; 127 if [-g setgid.txt ];then 128 echo"setgid.txt
is set-group-id." 129 else 130 echo"setuid.txt
is not set-user-id." 131 fi 132 chmod0755 setgid.txt ; 133 if [-g setgid.txt ];then 134 echo"setgid.txt
is set-group-id." 135 else 136 echo"setuid.txt
is not set-user-id." 137 fi 138 rm-f setgid.txt ; 139 #output: 140 #setgid.txt
is set-group-id. 141 #setuid.txt
is not set-user-id. 142 143 #-L file 144 # True if file
exists and is a symbolic link. 145 # [link
链接]同-h，存在且是符号链接时为true 146 #-h
file 147 # True
if file exists and is a symbolic link. 148 # 存在且是符号链接时为true 149 touchsource.txt
; 150 ln -ssource.txt
target.txt ; 151 SOURCE=source.txt
; 152 TARGET=target.txt
; 153 if [-h$SOURCE];then 154 echo"$SOURCE is a symbolic link."; 155 else 156 echo"$SOURCE is not a symbolic link."; 157 fi 158 if [-h$TARGET];then 159 echo"$TARGET is a symbolic link."; 160 else 161 echo"$TARGET is not a symbolic link."; 162 fi 163 rm-f$SOURCE$TARGET ; 164 unset SOURCE
TARGET ; 165 #output: 166 #source.txt
is not a symbolic link. 167 #target.txt
is a symbolic link. 168 169 170 #-k
file 171 # True
if file exists and its ``sticky‘‘ bit is set. 172 # 存在且文件属性中设置了t位时为true 173 TMP=/tmp
; 174 if [-k$TMP];then 175 echo"$TMP‘s \"sticky\" bit is set." 176 else 177 echo"$TMP‘s \"sticky\" bit is not set." 178 fi 179 unset TMP ; 180 181 #-p
file 182 # True
if file exists and is a named pipe (FIFO). 183 # [pipe
命名管道]存在且是命名管道时为true 184 #以下脚本需要以root身份执行 185 if [$USER="root"];then 186 FIFO=/proc/1/fd/4; 187 if [-p$FD];then 188 echo"$FD is a named pipe." 189 else 190 echo"$FD is not a named pipe." 191 fi 192 unset FIFO; 193 fi 194 195 196 #-r
file 197 # True
if file exists and is readable. 198 # [readable
可读]存在且可读时为true，注意不是只读 199 touch readable.txt
; 200 touch unreadable.txt
; 201 chmod444 readable.txt ; 202 chmod000 unreadable.txt ; 203 READABLE=readable.txt
; 204 UNREADABLE=unreadable.txt
; 205 if [-r$READABLE];then 206 echo"$READABLE is readable." 207 else 208 echo"$READABLE is unreadable." 209 fi 210 if [-r$UNREADABLE];then 211 echo"$UNREADABLE is readable." 212 else 213 echo"$UNREADABLE is unreadable." 214 fi 215 rm-f$READABLE$UNREADABLE ; 216 unset READABLE ; 217 unset UNREADABLE ; 218 #output: 219 #readable.txt
is readable. 220 #unreadable.txt
is unreadable. 221 222 #-s file 223 # True if file
exists and has a size greater than zero. 224 # 存在且不为空时为true 225 touch test_file
; 226 TEST_FILE=test_file
; 227 if [-s$TEST_FILE];then 228 echo"$TEST_FILE has something." 229 else 230 echo"$TEST_FILE has nothing." 231 fi 232 echo"something">$TEST_FILE ; 233 if [-s$TEST_FILE];then 234 echo"$TEST_FILE has something." 235 else 236 echo"$TEST_FILE has nothing." 237 fi 238 rm-f$TEST_FILE ; 239 unset TEST_FILE ; 240 #output: 241 #test_file
has nothing. 242 #test_file
has something. 243 244 #-t fd 245 # True if file
descriptor fd is open and refers to a terminal. 246 # [terminal
终端]文件描述符已打开且关联了一个终端时为true 247 # 可用于判断一个脚本是运行于交互模式（终端模式）还是非交互模式（cron或at） 248 if [$USER="root"];then 249 FD=/proc/1/fd/4 250 if [-t0];then 251 echo"File
descriptor $FD is
open and refers to a terminal." 252 else 253 echo"File
descriptor $FD is
not open or not refers to a terminal." 254 fi 255 unset FD ; 256 fi 257 if [-t1];then 258 echo"File
descriptor 1 is open and refers to a terminal." 259 else 260 echo"File
descriptor 1 is not open or not refers to a terminal." 261 fi 262 263 #-u file 264 # True if file
exists and its set-user-id bit is set. 265 # [setuid]存在且文件属性为"...s......"时为true，其中.代表-,r,w,x中的任意一个 266 SETUID=/usr/bin/passwd
; 267 if [-u$SETUID];then 268 echo"$SETUID‘s set-user-id bit is set."; 269 else 270 echo"$SETUID‘s set-user-id bit is not
set."; 271 fi 272 unset SETUID ; 273 #output: 274 #/usr/bin/passwd‘s
set-user-id bit is set. 275 276 #-w file 277 # True if file
exists and is writable. 278 # [writable
可写]存在且可写时为true 279 touch writable.txt
unwritable.txt ; 280 WRITABLE=writable.txt
; 281 chmod666$WRITABLE ; 282 UNWRITABLE=unwritable.txt
; 283 chmod444$UNWRITABLE ; 284 if [-w$WRITABLE];then 285 echo"$WRITABLE is writable." 286 else 287 echo"$WRITABLE is not writable." 288 fi 289 if [-w$UNWRITABLE];then 290 echo"$UNWRITABLE is writable." 291 else 292 echo"$UNWRITABLE is not writable." 293 fi 294 rm$WRITABLE$UNWRITABLE ; 295 unset WRITABLE
UNWRITABLE ; 296 #output: 297 #writable.txt
is writable. 298 #unwritable.txt
is not writable. 299 300 #-x file 301 # True if file
exists and is executable. 302 # [executable
可执行]存在且可执行时为true 303 if [-x$0];then 304 echo"$0 is executable."; 305 else 306 echo"$0 is not executable."; 307 fi 308 309 #-O file 310 # True if file
exists and is owned by the effective user id. 311 # [owner
属于]存在且文件的所有者为执行脚本的用户时为true 312 if [-O$HOME];then 313 echo -e "$HOME is owned by the effective
user \"$USER\"."; 314 else 315 echo -e "$HOME is not owned by the effective
user \"$USER\"."; 316 fi 317 318 #-G file 319 # True if file
exists and is owned by the effective group id. 320 # [group
所属组]存在且文件的所属组为执行脚本的用户所在的组时为true 321 EFFECTIVE_GROUP=`groups | cut
-f1 -d ‘‘` ; 322 if [-G$HOME];then 323 echo"$HOME is owned by the effective
group \"$EFFECTIVE_GROUP\"."; 324 else 325 echo"$HOME is not owned by the effective
group \"$EFFECTIVE_GROUP\"."; 326 fi 327 unset EFFECTIVE_GROUP ; 328 329 330 #-S
file 331 # True
if file exists and is a socket. 332 # [socket
套接字]存在且是套接字文件时为true 333 334 #-N file 335 # True if file
exists and has been modified since it was last read. 336 # 存在且最后一次读取该文件时改变了文件的内容时为true 337 touchtest.txt
; 338 TEST_FILE=test.txt
; 339 echo"test.txt">$TEST_FILE ; 340 if [-N$TEST_FILE];then 341 echo"$TEST_FILE exists and has been modified since
it was last read. " 342 else 343 echo"$TEST_FILE not exists or has not been modified
since it was last read. " 344 fi 345 sleep1 ; # 休眠1秒钟，否则看不出效果。 346 cat $TEST_FILE> /dev/null
; 347 if [-N$TEST_FILE];then 348 echo"$TEST_FILE exists and has been modified since
it was last read. " 349 else 350 echo"$TEST_FILE not exists or has not been modified
since it was last read. " 351 fi 352 rm$TEST_FILE ; 353 unset TEST_FILE ; 354 #output: 355 #test.txt
exists and has been modified since it was last read. 356 #test.txt
not exists or has not been modified since it was last
read. 357 358 #file1 -nt file2 359 # True if file1 is
newer (according to modification date) than file2, or if 360 # file1
exists and file2 does not. 361 # 当file1比file2新或file1存在而file2不存在时为true 362 363 #file1 -ot file2 364 # True if file1 is
older than file2, or if file2 exists and file1 does not. 365 # 当file1比file2旧或file2存在而file1不存在时为true 366 367 #file1 -ef file2 368 # True if file1 and
file2 refer to the same device and inode numbers. 369 # 当file1和file2引用相同的设备或具有相同的节点号时为true 370 371 #-o optname 372 # True if shell
option optname is enabled. See the list of options under
the 373 # description of the
-o option to the set builtin below. 374 375 #-z
string 376 # True
if the length of string is zero. 377 # [zero]字符串长度等于0时为true 378 379 #string 380 #-n string 381 # True if the length
of string is non-zero. 382 # 字符串不为空时为true 383 384 #string1 == string2 385 #string1
= string2 386 # True
if the strings are equal. = should be used with the test command
for 387 # POSIX
conformance. 388 # string1和string2相同时为true 389 390 #string1 != string2 391 # True if the
strings are not equal. 392 # string1和string2不同时为true 393 394 #string1 < string2 395 # True
if string1 sorts before string2 lexicographically. 396 # string1在字典中排在string2之前时为true 397 398 #string1 > string2 399 # True
if string1 sorts after string2 lexicographically. 400 # string1在字典中排在string2之后时为true 401 402 #arg1 OP arg2 403 # OP is one of -eq,
-ne, -lt, -le, -gt, or -ge. These arithmetic binary 404 # operators return
true if arg1 is equal to, not equal to, less than, less 405 # than
or equal to, greater than, or greater than or equal to
arg2, 406 # respectively.
Arg1 and arg2 may be positive or negative integers. 407 #
-eq equal
to 等于 408 #
-ne not equal
to 不等于 409 #
-lt less
than
小于 410 #
-le less than or equal
to 小于或等于 411 #
-gt greater
than 大于 412 #
-ge greater than or equal
to 大于或等于
